V1Valarob,
In a nutshell yes, and it does not have to be in a "N" reg aeroplane. However, there are restrictions, it has to be for someone working towards an FAA certificate, or someone who is doing a BFR or I.F. prof. I really don't think you could make a living in the UK doing this, not even close!!! There are also restrictions with pilots flying between England, Ireland and Europe in "N" reg machines without a valid FAA license, for which you can be used.