Ok. We moved our stuff over and were happy with doing so; we lived in London in a smaller flat than we expected (company package changed to a much smaller rent than we had been told about) so we ended up selling some of our things and giving some away on Freecycle. If you have something big that you're attached to and will have storage at home in the States, you might consider leaving it behind so that you won't have to worry about having to get rid of it.
If your budget is big and/or your in an area that's a little less expensive than some of London, then it may be that you'll have the space for whatever you want. Things are relatively expensive in London and I'd say in the UK in general if you consider the £ - $ exchange rate, so you won't want to be buying everything new --- unless, again, your budget is nice and big.
If you happen to be leaving from the NY/NJ area, we have some UK appliances that our movers accidentally packed, by the way. We're happy to give them a good home BACK in the UK.
Edit: I just noticed you're in CA.