Okay, now I have been working on the problem. VM, I found where the fridge's levelling feet are, while vibrating was happening..........and twiddled them with the appliance leaning on my shoulder Must have helped because now the door doesn't swing shut when fridge is upright and open again.
For good measure, I added a piece of underlay which is exactly the right size.
Now going to bed, and will hope tonight is better than last night when I got maybe a couple of hours sleep. I know it sounds funny, but once the sleeping pattern has been disturbed for so many months, you tend to lie wide awake, waiting for the next half hour session of rock and roll.
Viv