Have you asked the seller how the car was purchased/sold in Japan?
I had a car imported from Japan which was purchased through auction, Integra DC5, not a VW. If the car was sold through auction, ask to see the auction sheet as this will tell you how the car was graded. Although it may not be 100% accurate, it should give an indication if it had bodywork damage, mileage, etc.
Insurance shouldn't be an issue. Mine was garaged and a weekend car, and I was paying less than £400. The garage and being the wrong side of 30 probably helped with that premium though.
Tax, check what the owner is currently paying and what is on the V5. When importing it is down to DVLA to enter the details correctly which can affect how much tax is paid. On DVLA's first attempt they put down that my car was a pickup
Rust, my car was undersealed on arrival. Not that expensive but something to factor-in.
Clocks, there are a few companies out there who can do the conversion. Some will give you a BIMTA certificate, some don't.
There are also companies who can provide you with the cars history from Japan.