Peter
Each of us have proffered advice in response to your query yet you now ask
do I go through the hassle of sitting on the phone, waiting forever for the HMRC to pick up to tell them I have a tenant paying rent direct at under 100 GBP per week, or do I not bother and account for it on my tax return as normal?
This is not a technical query but seems to be a bit of a rant about HMRC.
My advice appears to me crystal clear and etf''s latest posting sums up the position as between us admirably, if i may say.
There appears to be nothing further to advise on.