Ian,
Can't help directly, although you know what VAT is so that should be pretty straight forward, and import duty is also a set figure for the UK and should be easily obtainable (not that I kow what it is, helpfully). I imported a car to Germany from the US and so paid Germany costs (their VAT, or mwst as they call it, is 19% but was 17% at the time). I actually paid about $1300 in total to ship the car, which included two road moves. One of 200 miles to Baltimore on a flatbed, and one from Bremen to where I live (another 150 miles) on a car carrier. The cost of actually shipping the car was $800 or so.
I just wondered if your forwarder/shipping agent was over charging and putting the blame on taxes?
JH