Dave
Kingstown Shipping in Hull are the people to talk to, either Alan or Mark (tell them Graham from MEB recommended you, I'll be on a commision soon)
The thing to watch is internal shipping costs in the US, Kingstown tend to ship out of LA but it can cost up to $1000 to get a bus to the port (washington State/oregon area etc). Shipping costs are approx £1350 for a single bus + UK Handling (usually £350) and Duty (Flat £50) and VAT on the purchase price and an element of the shipping, on my last bus it was just under £300.
So for shipping the bus itself and getting it into the UK you are looking at approx £2K + any costs in the US to get it to the port.
Sellers in the US can be funny about giving you their bank details but thats the best way to pay, don't use things like Western Union as its easy to get ripped off. If you want the name of a money transfer company drop me a pm and I'll give you some contact details. You pay them in Sterling and they pay your buyer in Dollars, all for £15!!