Liam Fox.

Liam Fox has argued for a return to the EU being merely a Common Market.

It can't and won't happen: it is a distraction and should be avoided like the plague. In the dubious unliklihood that it were ever enacted - it would be just the same as last time with power grabs and eurocreep but from a stronger base and massive sabotaging from the usual suspects!
A withdrawal to associate membership however, is a wholly different matter.