I'm not actually a great fan of mushy peas but they do seem to go quite well with some things (and I agree that the canned ones are acceptable - indeed, I quite like tinned garden peas and petit pois).
However I do remember that mushy peas formed part of one of the worst meals I've ever had. I ordered 'pie and peas' in a pub in Huddersfield, expecting it to be the same as in Sheffield (where it's meat-&-potato pie, served with mushy peas, which can be rather tasty). I'd not realised that the Huddersfield version is a hot pork pie (also served with mushy peas). When you heat a pork pie all of the fat and jelly oozes out and forms a congealed mess with the mushy peas. Ugh!