How to clean an oven

Is it just me, or do you also find that oven cleaners don't work? Aside from the fact that probably most of you don't attend to such menial tasks around the house (again, is it just me?), how often should it be cleaned anyway? I tend to use my oven a lot and favour the 'open roast' method, which of course results in huge amounts of hot fat splattering all over and coating the inside of the oven. But when you cook with an iron pot (or is it just me who does?), this very action is much sought after as it seasons and lays down a patina to give the pot a smooth, rust-free finish, preventing that metallic after-taste when cooking in the future.
I have used practically every oven cleaner known to man, including bicarb and vinegar, and the chemical versions give off such deadly fumes that to put one's head in the oven is to risk one's life. Not only that, but the next batch of scones will have a distinctly chemical flavour.
I have tried the cleaning cream that is currently being sold by those smooth-tongued, slick salesmen at flea markets. It sure does work there, but not a hope in Hades when you get it home. I recently cleaned out my cleaning cupboard and threw everything away.
Another thing nobody ever warns you about is that a popular white ammonia-based cleaner removes all the temperature markings instantly. No opportunity to proceed with caution. I know many people who have blank areas around the oven setting knobs. This can be remedied with a permanent marker or a 'before' photo stuck on the cupboard above the stove.
I will stick to the modus operandi I have followed for years: once the oven gets to a really past-it patina, I chuck it out and buy a new one. I did that recently. Anyone looking for a well-seasoned, perfectly usable, under-counter oven, with matching, unseasoned, gas hob? Give me a call.