Hi and welcome link above is a good place to start
UK car, cheaper to insure, easier to check history and no issues with UK fuel
Import, usually have a few more toys, more power, need to be careful with fuel, they run 102 octane in Japan, so need remap or octane booster
Plenty to choose from, it's a buyers market at the moment, there are some very used Imperza's out there, but there are some very good used Impreza's
Good luck with your search