I looked at a Danish and a German aircraft last year, before eventually buying a UK-registered example. On the surface, both the Danish and German machines seemed OK. In practice, getting either of them on the UK register would have cost £20K+. The Danish machine was a Super Cub on a Danish experimental CofA with inadequate paperwork to convert it to a regular CofA. This would have made it extremely tough, if it was possible at all, to bring it in. The German machine 'allegedly' had only 300 hours on the engine (which I don't believe actually), but the previous overhaul was >10 years, so it would have had to be zero-timed to get on as a G-reg.
My advice -- it is possible, but it will cost several thousand at the very least and quite possibly a lot more. Above all talk to the CAA about your particular purchase before you purchase it. That may save you a lot of heartache. Leon Winnert at the CAA is very helpful indeed.
QDM