There is also the issue of software on your US purchase laptop.
The Windows that comes with most US purchased computers, desk or laptop, is subject to some export restrictions. Because of antitrust decisions, the Windows you get in most of Europe is slightly different than what will come on a machine purchased here. I don't know that you'd have any problems taking your machine (and software) back to the UK, but it might be wise to ask your travel agent before you plan to far ahead. US travellers carrying US laptops to "foreign places" often have to make advance arrangements for the software, and sign lots of papers.
If you decide to bring a computer with you, you should check on ex/import regs at both ends before you finish packing.
A number of other programs that might "come with" a US purchased machine are likely to be subject to some export restrictions. Windows 98 "survives" only because it's illegal to export any later versions to China (and elsewhere), and lots of people there thus are still using Win98 (probably mostly counterfeit).
If you deal with one of the majors, it might be possible to order a computer from your homeland for "drop shipment" delivery at a US address where you could pick it up when you arrive. Ordering from home you'd likely pay the local taxes so the price advantage might disappear. I'd suspect you'd have to make a direct (email?) contact to investigate the possibilities.