Andy Burns wrote:
Another Dave wrote:

My wife has just been cleaning the gas cooker. It's seems to have
been a struggle and taken forever.

Oven Pride is a gloopy caustic soda solution, you pour half of it in a
strong poly bag, and put the shelves in it, for a few hours, agitating
and turning. You can wipe the other half on the oven floor if it
needs doing.

Obviously take care with the liquid ...

And leave overnight.