Does anyone know if this is possible?

I don't see why not, although it all depends on what the phd is for and if the new university will allow your credits to transfer. Talk to individual universities to find out.

UK PhDs don't really work on a 'credit' type system though (excepting the newer 1+3 PhDs where the first year is spent doing a masters, which will earn credits) so I don't think it's necessarily that straight forward. Your best bet is probably if your current research team have some US collaborators who you could work with to finish your research...