The NFL has stopped all cutomisers from altering customers jerseys. EPS was the best, but their contract is to do custom jerseys which you have to buy from them, so you have to spend around $225 - £300. It's outrageous really, as once the jersey is yours you should be able to do what you like with it. The NFL has withdrawn contracts from customisers who have broken their policy. So no one will do the work now.
There is no one within the UK who can do the custom work, believe me I spent ages trying to find someone to put a kit on a blank jersey I had and couldn't find anyone to do it properly.