I phoned the NY international field office(very helfpul). They gave me the contact details for Adam House in uk. He is very busy but extremely helpful. if you can be flexible in time and meeting place he can do all the paperwork in a few minutes. I went to farnborough. His contact details are in many pprune threads or from the IFO.
It was all very straightforward especially I was given the impression you could not easily do this in uk.
EB