Thank you for all your kind, understanding comments. We came home today after an over-nighter visiting Jane's mum in her care home in London and the house seemed very empty. We had a sympathy card in the post from the vets which was so nice it started us off again.
We've decided that Murphy was irreplaceable so we're going to give ourselves a while to get over him and then take in a mature, rescue cat when we're ready, in the Spring.