That the best way to clean them is with a large dish of boiling water, containing 2 or 3 chopped lemons with the juice squeezed into it, then put the oven on maximum temperature for about 45 minutes. 
Apparently you should then just be able to wipe it clean without too much elbow grease.
I haven't tried this myself, but will mention it to Mr P, (oven cleaner extrordinaire) who usually favours Oven Pride.
Backseat Driver, Former PM Tony Blair Reckons The Triple-Lock...




. Think I'll stick to Lakeland oven cleaner.
