Hiya,
I imported a 2003 F150 in 04 when the vehicle was 9 months old. We had to pay VAT and import duty and the vehicle itself was in the name of the previous owner - we bought it from a BMW dealership in Texas who'd taken it in Part exchange.
For your questions, so far as I'm aware you'll need to pay the 10% (dont know if that rate has changed) Import duty no matter what. The VAT element I think you may be able to get away with if it's shown the car/vehicle is over a certain age (i think it's 6 months) and has a previous owner listed to prove it's a 'used' car.
I remember posting a response to a similar question here, have a look through the search options -
Overall, I'd say it's only 'interesting american vehicles' that are worth importing here, if you have something like that, then I'd say consider it - but remember the petrol prices here, plus insurance will be a little higher, parts may take a little longer than normal to get, reputable USA service specialists are thin(ish) on the ground. However, all that aside, there are lots of US cars here, so could be an option to sell yours off over there and pickup something 'already here'
Else, to actually 'ship the car' takes about 3-6 weeks and is around £1400 ($2700 USD) with a reputable company (I know of a company and can pass details if you wish)
You'll need a SVA test (single vehicle approval) which is around £250-300 and you'll need to budget in for some parts to make the car UK road legal (think headlamps, a fog lamp, number plates, reverse light etc)
There is a website which lists all of this and lots of info but I just can't find it at the moment - have a little dig around the web
Hope this helps!
Cheers! Dennis! West London & Slough UK!