Easier said than done. I need to know these exchanges are safe, and the ability to move GBP somehow.
Well... Intersango are quite respected in the community AFAIK - you can chat with the guys at #bitcoinconsultancy over on freenode, and I also remember one of the guys who runs it doing a huge community Q&A bitcoin session on Slashdot a while back.
With regards to the GBP issue - could you not just cash out bitcoins whilst the rate is high, and then buy additional bitcoins when the rate drops more in line with other exchanges and transfer the bitcoins directly back to mtgox or whatever? Intersango has no deposit, withdrawal or transaction fees, so it would make profit more feasible on slimmer margins....
Either way, I hope this helps someone - I am sad that I chickened it and cashed out my BTC earlier when I saw mtgox drop