What I mean Clifford is that unless you know what you are doing with the strong chemicals used in the oven cleaning process, then leave well alone.....pay a pro to do it for you.....(but then again I'm biased that way!).
I certainly would not advise anyone to purchase any of the decarbonising gels and sprays without that individual having undergone at least some sort of Health and Safety training in their use....some of that stuff can blind you in minutes...too big a risk, I would find it hard to deal with if, through my "advice" someone was seriously hurt.
There are some so called "safe" products on the market but not having seen the COSHH sheets for them I couldn't guess how "safe" they would be (Mr Muscle/Cilit Bang etc etc)
Hope this clears things up a bit. (This is only my opinion..if someone else wants to advise someone differently..feel free).
Tom