Depends on car for getting on the road due to SVA test (car over 10 years old do not require SVA test) If you buy a well modded car you will have to virtually put it back to std to get it thru the SVA test, I sva'd 4 cars last year (Evo 7, RX7, Skyline R34 GTR and a Subaru Legacy) 3 passed straight away as they were still std and the RX7 was a headache (cost £1000 for RX7 specialst to get it thru)
£1500 for shipping and insurance
VAT @ 17.5%
Duty @ 10%
In other words a car which costs you £10,000 in Japan will cost you just over £14,000 b4 any SVA, MOT etc etc