There are different figures we are talking about here and to be specific. To break it into the simplest terms, there are 3 figures.
1 - General Damages
This is what is known as the personal injury part. So whiplash, scars, broken neck, leg amputation. All that comes under this umbrella.
How do they quantify this figure? There are 2 main sources.
A - Kemp v Kemp, this is a volume of case law that is updated every year with judgments from the Courts on the latest damages award for all the personal injuries you can think of. The folder categories the cases by injuries. So you have a client with tinnitus as a result of an accident, you can look under that. It then have brackets for damages depending on severity of the injuries. How they define how serious an injury is? That is down to the expert, normally a Consultant in a specialist area of medicine.
B - Judicial Studies Board Guidelines - This is similar to the above, each injuries has brackets and between the 2 of them will give a fair indication on the value of the injury.
The insurance company also have a database and algorithm to calculate how much a claim is worth, this program/super computer works out all the variables and suggests a bracket that the case is valued in and they allocate a "budget" for this claim. Obviously if someone has brain damage then the value will be higher. This figure is normally very accurate from the figure a human (claim handler/lawyer) arrive at after reviewing the file and all the medical evidence. Of course it can also be adjusted and increase or decreased if further evidence comes to light - such as if the claimant develops chronic pain syndrome down the line or caught he was working when in fact he wasn't.
In reality, death is cheaper to the insurer than someone seriously injured.
To quantify this, if they so wish, they will check his background by requesting his GP records, hospital records, x-rays, MRI scans and even employment personnel records. These are all disclosable under the CPR.
For example if there is a claim for lower back pain for £15,000. And his GP records shows he had degenerative back problem for the past 5 years and this accident has accelerated its symptoms. The value of the claim would be different than a person who has never had back problems and the accident is the sole cause of the back pain. The quantum of this will depends on the severity of the original symptoms and how much it has accelerated by (number of years), again, expert evidence, this case would be a report by an Orthopaedic Consultant.
2 - Special Damages
This is the stuff that can be replaced and quantified by money. i.e. car, clothes, loss of earnings, medical bills, travel costs etc. It is also the more expensive part in the bigger claims.
Everything claimed under this will be subject to proof, for the most part*. However, there is a maxim in Equity that there can be no betterment. So if the car is worth £5k, he will get £5k, or its market value, he won't get a new car as a replacement. The reality is that they will make him a low offer (its tactics) to begin with. It is only logical that the insurance will want to pay out as little as possible.
Heads of damages like salary, depending on amount and duration claimed, will require payslips, P60, letters from employer, accounting records, HMRC records, bank statements etc to prove earnings. The insurance company will not take the claimant at his words. They will check with DWP to see if there are any benefits and deduct it if there is (so there is no double dip). The claimant will be paid what he would have got paid if he went to work as before.
Of course, if it is a serious injury, say for example someone who is 25 years old, 1st Class degree from Oxford and is a junior stockbroker at a prestigious firm in the City and his career was cut shot in a car accident. Now can't work in his chosen profession and paralysed from the neck down. His prospect of a long successful career is cut short. They will claim loss of earnings, as projected by employment experts on how much he could earn in his career until retirement age. (both sides will have their experts) This of course is an extreme scenario, but that is the basis on which it is claimed and how the system works.
Again, there can be no betterment. I cannot stress this enough. On paper it will look like he gets millions and millions, but that is what he would have got if he continued with his career as any other stockbroker would. Besides, if you are this guy, choosing a life paralysed with millions but need someone to wipe your bum or living to the full and earning your millions...what would you choose?
There are other things such as gardening costs, DIY, medical costs, or wheelchairs. Pretty much everything you can think of, things that he would have done himself but now has to have hired help.
If the Claimant has died and there are children involved then there will be a dependency claim (up until age of 18)
*On the less serious side, if the claimant claims £50 for broken sunglasses, and can't provide photos or receipts. Then on this instance the insurance company may make a gesture of say £20 to pay off this head of damage. In this instance it is more economical to pay it off then argue over it.
3 - lastly, the legal cost. This is where you and the Claimant don't see. And can drag on for months after he gets the cheque for his whiplash.
Of course, the system is not infallible and this is where people, as human nature, take advantage of it. Be it a fake claim or simple exaggeration on the injuries. This is where the bad reputation comes from. The design of the system is not to award the Claimant for his injuries but to compensate for his loss back to if the accident never happened.
On the whole, you will only see 1 figure, the figure where General and Special damages combined and it will often look like someone got a huge payout for something relatively minor.
So in your case, whiplash - £750 to about £2,500. plus a couple of weeks off work (if he is a contractor with no sick pay), plus damages to his car, plus car hire if there is any, policy excess, plus NHS prescriptions, travel to hospitals or GP (taxi etc), plus there may be care and assistance....lets say he needs help dressing for 3 weeks as he has neck pain and can't lift his arms, claimed 1 hour per day at £6.75 per hour. It will all total up with a figure.
It is never "I have a sore neck, now give me £2,000" and then pays up. Although it is probably cheaper that way since it saves legal costs! It is always in the Claimant's Solicitors' interest to drag it out as long as possible, it is also more "lucrative" if they issue proceedings as they get more what is call success fee. The Defendant on the other hand will want to get rid of it as soon as possible (for legit claims).