But as far as the sender knows he did, they delivered it. If something was wrong they should have brought it up straight away and provided proof before delivering it.
You would have to be a total mug to pay this extra £43.
I don't know the exact details but I assumed it was one of those websites where you put in the details and the courier comes to your door, all the 3rd party really does is offer you a price comparison website and booking service. Parcel Force will just take the parcel and then measure/weigh it at the hub and if there are any discrepencies ask for more money from the customer (in this case the 3rd party). Like I said I'd ask for proof of the invoice from Parcel Force though because it could easily be the 3rd party trying it on.
