Pear tree cordons

There used to be a small pear tree in my garden until last year (a Comice, I think), which never, ever grew. It had been in the garden since I moved in, in 1981 and quite possibly for much, much longer as our large apple trees are 1940's varieties. The pear would bear half a dozen fruits, rarely more, and as I said, never really grew. We dug it up last year and replaced it with a plum, and found that the roots were very poor.

I have space for two oblique pear cordons in my garden. I am in SE England, and they would be quite sheltered. I garden on fairly heavy London clay. Does anyone know what varieties might thrive, both on the soil and to grow as cordons, as I would be disappointed to have a repeat of the late tree. My only proviso is that it has to be a pear that ripens to a soft texture - I absolutely hate crunchy pears. My favourites of those available in supermarkets are Williams (green or red), Taylors Gold and Comice.
Any suggestions or advice gratefully received.