I have always had jap cars, prob 50/60, and at least 6 imports.
I have usually had a quick look around for other quotes, but every time A-Plan is best. These internet companies and supermarkets may look ok, but are stuffed full of clauses, conditions and high excesses. A Plan have special dept, based in Thatcham, mostly dealing with imports. In my experience, the companies they use also dont seem to bothered about mods, (but its worth letting them know anyway, to get it confirmed)
Give them a try. Also I would agree, theres not not usually a huge increase for a turbo, well not proportional to the power increase !!
Ive had non turbo's, and always found that even with the usual bolt on goodies, I always wished Id gone for turbo in first place!!!
Anyway, as someone else said, dont give up, you wont beat the toyota for reliability, great looking, holding its value, and generally being awesome fun!
good luck
davep