What's the safest way to buy bitcoins in the UK? I have come across multiple websites offering bitcoins for UK bank transfer. What site have people had the best experience with?

I've come across a few so 

www.quickbitcoin.co.uk

www.bitbargain.co.uk

www.blockchain.info

Ideas?
The safest way (though perhaps not convenient) is to create a two-party legal contract with signed witnesses. This way if either party reneges you have legal recourse in the civil courts. The contractual arrangement would be somewhat similar to when a freelancer charges bitcoins for their goods or services.

Escrow doesn't provide the same level of protection, as your legal contract with the escrow company (if any) usually includes a clause that final binding arbitration is made by the escrow company - not you. However, a reputable escrow service or currency exchange will typically suffice for people with moderate risk appetites.