[Margaret Pilkington]

Less, oh dear.....that really sounds like a recipe for disaster.
Not that I am sure that I really believe your version of events(after all this IS anything goes).
I am not going to volunteer to be your cleaning lady......I have enough on. What with doing the cooking for Ma, doing her bag wash and running the vacuum over her carpets when she is feeling a bit limp.
But.....I will give you a tip.
This is for those dishes that are crusty with baked on food(I have no doubt that this would work equally well on the inside of the microwave).....a bowlful of very hot soapy water(the washing up liquid that is on offer at Asda will do for the bubbles).....into this goes a scoop (or a tablespoonful) of soda crystals.
Dunk the offending dish in the water for a few minutes and all the crusty baked on food should come off with little effort.

Now obviously you cannot dunk a microwave in this solution, but what you can do is put some of this wonderful liquid(well, it is wonderful as long as you don't try to drink it) into a squirter bottle(let the liquid cool a bit if you don't want a melted plastic bottle on your hands) and squirt the inside of the microwave with this liquid(not too much or it will just run out onto your counter and the floor).....leave it to digest the grime and then wipe inside the microwave. This should do the job Less.