Once a CORGI person has connected up a gas cooker with the usual flexible
hose into bayonet fitting, is it sensible for the average DIYer to
occasionally disconnect it in order to move the cooker out - eg to fit new
flooring - then push it back in and connect it up again?

If you absolutely check that the bayonet fitting has totally cut the supply
and there is no smell of gas afterwards, then you should be OK for short
supervised periods when you are in the house, such as to do the job in
question. When I got my tame CORGI (Hi John!) to connect my bayonet, I
ensured that he installed an isolating lever valve at the same time to cover
the outlet. Therefore, I can be somewhat more confident when removing the
cooker, even for long periods when I might not be present. It is good for
holidays, too, even when the cooker is connected. There can be no more "did
I leave the cooker on" when you are 100 miles down the motorway when you can
remember an unusual event such as turning off a lever valve, even if it does
confuse the wife shortly after your return.

Christian.