Thought I'd update this on an n=1 basis, since after 4 years I've finally tested positive:
No temperature, sharp headache occasionally, scratchy throat, runny nose, achey muscles (especially the sort of places where I used to get the same when I had my period, plus neck), occasional sharp, hacking cough. Spent yesterday evening (day 3) lying shivering on the sofa and starting to wonder whether this was something more than the heavy cold or possible light flu that I'd originally thought it was. "T" bar still showing up quite clearly when I did the LFT after the end of 4 days, so I guess I'm not through it yet. The muscle aches in some ways were the worst: I couldn't find any way of lying in bed which was comfortable and would let me sleep.
EDIT: Balance issues also a problem. I initially thought I might have got an ear infection, especially when I climbed a two-step set of steps and then suddenly couldn't get down again from them! Not helpful when you're trying to replace lightbulbs!
DOUBLE EDIT: Forgot to mention that I've been really dehydrated despite - I thought - drinking a lot. Mouth and lips have felt really really dry. Unsure whether this might be related to a loss of smell?
Hoping I somehow haven't passed it on to my caree ...
Also somewhat worried that the NHS symptoms page hasn't been updated for 10 months. Seems as though nobody cares these days.