I can’t remember where I saw it, but I recall reading that for at least some people admitted they are in hospital longer than before - they’re typically younger and therefore their bodies have more reserves to draw on if they become seriously ill.

My suspicion is that a single average (mean or median) will not be very insightful without stratification at the very least into vaccinated / non-vaccinated and probably by age too.

I’m also not sure how widely this data is available on a national level between various trusts. If it isn’t, on the assumption that the patterns of infection to admission/discharge and serious illness vs mild illness are holding roughly steady, the changes over time in the data published by the government about hospital utilisation (number of beds in use) are probably a good enough approximation for most purposes. If they stay manageable, with relatively low rates of increase over time, that’s a very different picture to them increasing dramatically in a short period of time.