http://www.sjdaccountancy.com/documents/sjd-stepbystep-contractors-guide.pdf
http://www.contractoruk.com/
http://www.pcg.org.uk/cms/index.php
That's pretty much where I got all the information I needed to make the choice to start my own limited company having been established as a contractor with an MSC. MSC's don't, or shouldn't, exist anymore. As you say, this leaves the choice of going through an umbrella company, or having a limited company.
Using an umbrella is quick and easy, it just isn't as tax efficient as setting up on your own. Be careful in selecting your umbrella, as there are a number of less scrupulous companies out there that could land you in hot water. Additionally, some agencies, particularly the larger ones have an approved list of umbrellas, which can mean that you have to switch companies if you get a job you like with an awkward agency. On the plus side, the admin usually extends to an electronic timesheet/expenses each week. You will pay them a weekly fee, which will include your insurances, and payroll admin charges.
Generally speaking, limited companies are best as a vehicle for keeping the most of your money away from Darling's sticky mitts. There is more admin involved, but that can be minimised by hiring a good accountant. There is a lot more reading up to be done by going limited, whereas you can be set up with an umbrella in a couple of hours. It will also take time to set up a company bank account, which will mean that you will not be paid until that is complete.
IR35 is complicated, but basically it is a legislation that was brought in to stop people calling themselves contractors, or having those tax benefits while not really doing anything that a normal permanent employee would do (providing own laptop, phone, car, toolkit, having insurances, and various other bits and pieces). If possible, make sure your contract / job is outside the remit of IR35 (ie, you're considered a legitimate contractor) as the largest benefit of being a limited company director is the ability to take a dividend of the companies profits. You pay yourself a salary, (usually minimum wage or similar) and pay any other expenses (accountancy fees, insurances, mileage, etc) and then whatever is left is the company profits, and is taxed at the small business corporation tax rate of 20% (this year) and the remaining amount can then be paid to the director(s) (you). The overall benefit is that the 20% tax rate is significantly lower than paying Income Tax and National Insurance (33% combined this year) so you keep more of your money. There are also other perks like Flat Rate VAT etc that help things along too.
Based on £27k (15 per hour, 7.5 hours a day, 5 days a week, 48 weeks a year) and assuming a scenario where the office is only 5 miles away, so you aren't out of the house for more than 10 hours a day, with no magazine/other subscriptions, not buying computers / furniture, not buying related courses, stationery etc (these will all boost your take home because you claim the expense back tax free. Beware companies that try and sell there services based in this dispensation, they will exaggerate the numbers to make things look better than they are) but with a £30 per month company mobile, and a £20 per month broadband bill, plus insurances, accountancy fees etc, I'd estimate your take home would be in excess of £1750 a month, plus an extra ~£100 in if you're on the flat rate VAT scheme. This is higher than the PAYE/£27k take home of £1673, and you wouldn't earn £27k in the same job as a permie anyway.
A word of warning though, be prepared to travel. Also, don't "sign up with a few agencies looking for IT engineer/technician or related work". Look for work on Jobserve / CW Jobs / others, and apply for them, regardless of the agency. While you're getting established, call the agency afterwards to chase them up, don't wait for them to call you, it may never happen. The key to being a successful contractor in the early days is staying in work.
You will also find that unless you're either immediately available, or can start next week, people generally won't want to know. This makes the last few days / weeks of a contract extremely nervy if you have financial commitments. When I started contracting, I used an umbrella because I didn't want anything to do with the paperwork, if I was doing it all over again, that wouldn't be an issue, however it might be smart to consider getting some experience of contracting to see if you can hack it / enjoy it before you commit to the annual insurance bills etc associated with going it alone.
Either have money behind you, or have a whopping overdraft. Never put you or your credit rating at risk by trusting a third party to pay you bang on time. It's usually fine, but you bet your ass that when something slips, it'll be at a difficult time.
Good luck!
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