Depends on how much you want to use.
I bought 100ml of 54mg base from ltecigs for £14 +P&p http://www.ltecigs.larsentilbrook.co.uk/index.php?route=product/product&path=61_84&product_id=488
or if you want to get a litre, better off getting some 72mg from the US
edit, here is link for the US site http://www.nicvape.com/store/c/20-Unflavored-Nicotine-Liquid.aspx
max strength allowed into UK is 75mg,
thanks for the reply ive bought nic from ltecigs before looking like i will be going bk haha