Teacher here too. Not had a letter, which I am a bit surprised about as a Type 1 with asthma (which has been well controlled for several years, but put on a steroid inhaler before Christmas as peak flow has dropped a bit recently). A few colleagues have had Covid and struggled with it - all are younger than me, with no health conditions and said symptoms were fine until the last couple of days when they became exhausted and felt more ill than they ever have before. As they contracted it during lockdown they said that it was lucky they were working remotely as there was no way that they would have been able to return to a workplace at the end of their isolation period.
I have quite bad cold/ flu symptoms at present. A test for Covid came back in 12 hours (!!) and was negative. BG levels are all over the place too.
A friend was in a conference call with a government minister a few days ago and was told that schools are not going to be rushing back this time around - probably up to Year 2 in early March, with older Primary year groups and Secondary holding out until infection rates and hospital admissions drop, which may well mean a post Easter return could be on the cards for some.
Whatever you decide, remember it is the right decision as it is yours. Some schools HR and Leadership teams have not really followed the rules or behaved in a sympathetic manner when it comes to protecting teachers, so make sure they don't sway your decision or put any undue pressure on you.