If you haven't contacted them already you could try the Bristol harbour master to see if they have any winter mooring spaces that were not taken up or Bristol Marina (within the harbour). Other than that - Bath Marina, Saltford Marina, Keynsham Marina, Phoenix Boat Yard - Keynsham and the offside moorings at Hanham might be worth trying. Lots of people CC around Bradford and Bath, lots of close stations at Trowbridge, Bradford, Freshford, Avoncliff and Bath. It's a bit of an enforcement hotspot so need to stick to the rules. Great community - see the Facebook Group and the Kanda Community Website.