I was eying up several ISF's over the first lock down and distinctly remember a black late spec one (central rev counter) with just over 100k being offerred for £17k it took several months to sell, pre-facelifts were around the 13k mark even less - prices are strong however the next month or so will dictate are buyers paying for the cars or not as cars at the bottom end of the market have shifted. E92/E90 M3 aren't selling either alot of stock dealers are holding atm. Personally I think the prices will come down a little but not low as pre-lockdown levels. as others have said the road tax and fuel pay a huge part esp if were heading to the not so magical £2 a litre.
I recently bought a ISF and its not had the Radiator done, I shall be getting it done as a preventive measure, during the mot I did ask and had a look myself and the pipes looks like they had oxidation but not corroded away - either way its getting done! I do have a receipt for the waterpump which is great.
Also going to get the arms, sills and underside wire wheeled and clear coated to prevent rust, luckily its quite clean but having owed Japanese cars most of mylife they are known to be rot bags!