The same basic rules apply to the UK, as to other countries.
For cars that are older than 10 years, no SVA test is required (a test done after arrival in the UK).
Cars younger than 10 years old (to the month of registration in Japan) require an SVA test on arrival in the UK
Cars are exported by RORO (roll on roll off car carriers)
The main ports of call by the shipping lines are Newcastle, Bristol, Southampton, Grimsby
Main shipping lines presently used are Armacup, Hoegh, K-line, Yusen