I have never actually imported a car to the UK - although I have thought about it a number of times. My brother in law went to Germany to buy two Porsche's a few years ago as there was a HUGE waiting list in the UK. Flew over, bought a couple of 6 month old ones from a dealers forecourt, drove back, had the lights etc converted and registered then sold one for almost double what he paid for it! I am not sure about the duty on second hand cars but I am sure a quick surf around the HMRC web site will give you the outline. I think you would save a bundle (depending on what happens to the pound in the coming week(s)) otherwise there would not be such a booming market with Jap imports in the UK, just depends if you are prepared to go through the hassle of importing (which most people won't hence the reason car prices are higher in the UK than most of Europe)......
As for UK market price for a MK1 b the following is my opinion based on the cars that I have seen/nearly bought;
£1950 - £2500 - early car with high miles, some history - but overall shabby
£2500 - £3500 - highish miles but fair condition, service history but base models
£3500 - £4500 - lower miles, service history, good condition, comfort pack (leather etc)
£4500+ - MK1 'minter' FSH, clean and rust free, good spec, low miles etc.....
There are motoring guides out there that disagree with my opinion but I have seen b's on the Autotrader up for £4k+ in 'ok' condition that have been there for over a year! When you consider you can pick up a mk2 for £5.5 a mint mk1 'aint gonna fetch much more unless it goes to someone like us who are looking for a specific model/year mk1.........