NFF_PRF
You need a letter from the CAA (yes you have to pay) saying you have the experience etc, a copy of your license is not enough, you need a letter from an operator of N reg a/c to say that you work on them. You then have top pay around £85 to the local faa office, Gatwick in the UK, who WILL interview you and say yes or no. They then give you 3 slips of paper that entitle you to take the written exam, these are valid for 2 years. Which there is a place in the UK where you can do it, otherwise the USA, then you have to do practical/oral exam at an FAA testing center in the USA.