Have you thought about seeing if there is a local sheltered housing scheme where there may be some residents who would love to get out and about for a walk but feel the same way as you and dont want to do it on their own? Often they can be isolated and would relish some company and possibly some exercise? Even half an hour a week could be invaluable for some people - it could be the only contact they get!
Thought I would try and encourage all you shrinking violets to leave a message, I'm a 'nearly gran', my grandson is not due until June. Hating this cold and grey weather as my plants are not growing but would like someone to walk with. I live in the Chew Valley, hoping to speak to others soon