Should have mentioned that for any US Dollar investors contemplating UK investments I'd suggest perhaps holding off for a while yet.
'Quantative easing' - or printing money is likely to drive the USD/UKP more closer to parity over the next year or so IMO.
It's a bit of a race as to who prints the most, my guess is that as we're in more of a bad state than the US that we'll win that race.
Get the timing right and you'll perhaps be able to benefit from a good yield and currency benefit (I believe historically long term the pound/dollar has typically ranged from near 1:1 up to 1:2)