ok, i'm heading off to the good ol' USofA next month, and plan on spending a fair bit of money on bike bits. Looking to pickup some wheels/rims and possibly a frame along with lot's of other smaller stuff.

Anyone recommend a good/cheap way of getting everything back to blighty? Not sure what the deal is with customs - am i likely to get stung if I try and stash everything in a suitcase and not tell them.

Take all the price labels and packaging off things, and claim that it's used but you bought it all over to the US for refurbishment. Customs can only tax new items and not things that are second-hand/used.

Just box everything up as well as you can (esp wheels and frames) - lots of shops in the US will box bikes for about 40 USD. If you want to do it yourself, shops will generally sell/give you shipping boxes (on my last trip, I picked up a box, padding, spacers and assorted rubber bumpers for 5USD from a shop).

Most international flights you can bring boxed bikes on with no problems. Have done this with Virgin and American recently. The bike just formed part of my normal baggage allowance. Flying with your bike is much safer than shipping it and its my preferred method.

Customs - you have to pay for anything less than six months old as damnham stated. But your chances of being stopped at Gatwick/Heathrow are really slim. They tend not to stop passengers from US flights, in my experience.