Rob,
I shipped my car from Los Angeles to Southamption in January. It arrived with no damage and is now registered/insured but there were a few things I learned along the way.
You can get a 'Binding Tariff' classification for the car from HM Customs and Excise before you ship it (+44-1702 366077) or (classification.tso@hmce.gsi.gov.uk). This is the document that values the car for import duty and VAT. Until recently, any car over 30 years old was deemed 'historic' and exempted from tax. BUT, now HMCE are using a new definition of 'historic' and they argued that my 280SL was one of 23885 made and therefore not eligible for exemption.
Even though I owned the car since 1982 I was still liable for 27.5% tax (duty 10% plus VAT 17.5%). I minimized the damage to the pocketbook by submitting a Bill of Sale for $6,500 USD (rather than market value of £25K+). They accepted it
The car was driven on a lorry to my house by the shipping company for a nominal extra fee (approx £100) which was good value since they also handled all the necessary documents to release the car and saved me the hassle of driving/insurance/police/etc.
Insuring the car requires a registration numer plate (although the insurance company can issue a policy temporarily without one) but registering it requires a valid MOT. This is not straightforward since the US spec will not pass without mods to the lights/wiring(headlights, running lights, brake lights). Find a garage who does this a lot and it shouldn't cost too much (approx £200-250).
Registering the car at the DVLA office is easier if you bring the US title deed with the previous owner's signature. Do not let the previous owner send the title deed to his/her state's licensing office (which they would normally do). Make a copy of the title deed for your records because the DVLA will not give it back to you.
Find a specialty insurance broker to get a good deal. I pay £165 per year for comprehensive coverage (3000 miles per year).
You will then have an EU registered car and can move more easily to other EU countrie i.e., no duty. But to register the car in, say, Spain, you will have another set of registration/insurance processes to navigate. Unfortunately, I haven't cracked that one yet.
Contact me if you want the names of the shippers/garages I used.
Good Luck
Ion
1971 280SL automatic