If this is a long term situation, using todays prices is definitely not the way to go as I suspect the prices are heavily reduced because of the lack of demand from tourists. Pure guess, but I think you will probably see sub-£100 midweek rooms for as long as international tourism is surpressed. How long that lasts is anyones guess...next year maybe?
Pre-covid, you'd be lucky to find accommodation sub-£120 I reckon and even those wouldn't be central.
Long term, your cheapest options might be to find somewhere close to a tube line in zone 5 or 6 and away from places like Heathrow. You might find those hotel rooms cheaper, have free or cheaper parking and the total cost including an oyster tube fare cheaper than a central London hotel. Typical journey time will be 40-minutes to a central London location.