The advent of the Elizabeth Line has made staying at Paddington slightly cheaper if you want a direct line to Heathrow, but in relative terms it doesn't really make any great impact on the cost of a central London hotel compared to staying near the airport. I suspect there are actually very few people who would take this option - it's extra cost and extra hassle because you need to make two journeys. I would also say it's the riskiest option, albeit not a particularly big one - the train lines into Heathrow see issues far more often than buses fail to arrive and it's not unusual for services to be reduced to 30 minute intervals.

The Norfok Towers hotel you mention is between £150 and £250 per night over the next month or so. A Heathrow hotel would be in excess of £100 less than the average.

For people travelling with small amounts of luggage, the TfL buses are fine - you can usually find a spot around the wheelchair areas to stand for the few minutes it takes. Ditto the Underground from T4 or Hatton Cross which will usually be pretty much empty by the time the Piccadilly Line gets beyond Hounslow.

For anyone who has multiple pieces of luggage, a taxi or Uber from any of the Bath Road hotels will be about £15 including the terminal drop-off fee. That's still far quicker, more reliable and cheaper than a Paddington hotel.

The only reason I can see to staying at Paddington the night before a flight is that you're already there having been in London for a few days and don't want to move.