I wouldn't say only a few people have more than 1 bank account - rather a high proportion,even a majority do - based on my own circles but also forums like this,mse, refinery, fb, etc.
But the point made that we're a country of 2 halves is fair enough. The section on the MSE open University on saving says that even in the "good" years British people saved way under the EU average ( as percentage of earnings - something like 0.45% compared to average of 8% and high of 13%. Obviously the people who were struggling to save anything then are likely to be even worse off now and need to be the focus of any help that gets provided.
But....there are also a huge proportion of people who could have saved more but prioritised other things. E.g in the last stats before covid (2019) the average brit took 1.9 holidays abroad. If you take away all the people that didn't go away at all that's a huge percentage of the population who went abroad more than 2 or 3 times a year -so could easily have saved £500 or more just by dropping ONE holiday. That's not even looking into the stats abkht increased car finance, the number of people with the highest end smart phones etc...i.e. easy cuts you could make without limiting your lifestyle if you wanted to prioritise saving.
So its not as easy as just saying "people would save more but they physically cant" if people in much poorer countries do manage on average to save much more than us. We need to help the absolute poorest who actually can't save, but (as a pp said) then provide much better financial education for the vast majority who could save but have never been taught to prioritise it and then end up screwed when the really hard times come.