Excellent and timely advice, Cambo Thankyou. I'll come back to re-read it again nearer my departure.

Yes, 83 and with worsening osteoporosis. First trip in 3 years. I've taken care to pad the journey with extra time as I do everything much more slowly now. I hadn't thought of a taxi from my hotel attached to LHR T2 to the Central Coach Station but I suppose the hotel could arrange that, though taxi drivers might not want to do such a short journey. And in the reverse direction it's possible that taxis are not easily found within the coach station.

Flying J on SQ it seems a pity not to enjoy Book the Cook options, but your advice about food (and drink) is sound. I'm visiting my sister in rural Wales and intend to have a very lazy time there..