Thanks very much everyone for the replies. Whilst I knew withdrawal fees would factor, I hadn't considered that they would be that much. Presumably it's a static fee and doesn't multiply based on how much you are withdrawing so I'm happy enough to leave up to £100 maybe a little more on it I think.

Aside from localcryptos and localbitcoins, do you have any other suggestions for reputable places to buy from that don't have high withdrawl fees, or for decentralised p2p have good security for both buyer and seller? Where are the preferred non-exchange places to buy from?