If you are qualifying as a Peadiatric nurse rather than a RGN, you may have to complete an adult qualification, because the US do that very differently, they don't split in to branches (as far as I can gather) till after qualification, plus most American Nurses qualify able to do tasks, that UK grduates require post Graduate training for. (such as nursing diagnosis, IV canulation, and I think much much more)
All the agencies that will help you sort out sitting the USA exams, and Green card etc require at least one years experience in the UK, prefferable in an acute setting, I don't have the web addresses in front of me but if you check out the job sections of Nursing Times, many of the international relocation agencies have web page addresses that you can look at.
If you really do decide to work abroad, your qualification may be recognised in all of the European Union, (I know this is the case for the M.A.D course, but are you completing Project 2000?) And many places where there is a large British forces base have English speaking hospitals and schools
, such as Germany and France, which is a little bit closer to home than the USA.
I hope this helps some and hope you manage to find all the information you require to make the best choice for you.
Whisper, (Fellow UK student Nurse)