there are many "no mooring" signs on the little wharves that are behind lifting bridges, but the majority of the basin is free to moor.
There are lots of places near the ymca, and back towards the viaduct, the entrance to the basin is usually free, though has quite a high wall, and there is space for four visiting boats near the grocers warehouse.
A lot of us have put signs on our moorings (bridgewater approved ths) saying they were private, personally mine says "Private Mooring, NB Helena will return ________, please feel free to moor here until then", I'm trying to encourage others to do the same.
A couple of times a year the Lymm club "invade" the Basin with around 20 boats, and though they do breast, they all seem to get in.
Bex
I should add there is always space between locks 91/92 and I have never heard of any trouble, it's a pleasant place to moor with the cottage on the other side and the gardens, and is safe, though can be a little noisy while the restaurant is open.