BRITAIN has never been too keen on tying the knot with Europe. It sat aside in the 1950s as Germany, France, Italy and the Benelux countries forged a single market in coal and steel, which became a broader common market. It eventually joined, in 1973, largely because Europe seemed to be where the money was. Britons still think of their relationship with Europe as a transaction. But their feelings about the costs and benefits of membership have changed utterly.