I think it would help to elaborate on why you can't still potter around alone, what would happen if you just got on with something? Would he hang around, try and join in, interrupt, would he complain?
My DH and I work opposite shifts but no where near retirement age, I feel suffocated sometimes at the weekends when we are together all the time, so totally get it, if you are used to your own space/time it is hard to adjust, I am usually able to go off into a space in the house and just get on with things, I could watch TV in the bedroom if he was watching downstairs etc, we both seem to understand that we need alone time so it works out okay.
One of my family members however is in your shoes, she works full time, and her older DP has retired and he is always just THERE, no hobbies, no interests, no friends, he can't wait for her to get home from work, she is his emotional support animal but if she ever says she needs alone time for herself, he looks hurt at the thought, so she never forces it.. I find it so odd that he just doesn't care what she needs, it's selfish to be honest.