We called ours a George Formby grill because it was farcical. Oh, it cooked well enough, but the hassle of cleaning it afterwards was absurd, plus all the grease to get rid of.
We rapidly reverted to our old cast iron griddle-plate...you can get one from Kitchen Craft for about twelve quid...which does precisely the same thing. Its great beauty is that all you do when cooking is finished is pour about an inch of warm water into the sink and lob the thing in. (I'm not sure how the plate would work on an electric cooker, but with gas it's fine.)
Obviously, it doesn't have a lid to cook from both sides, but turning things isn't really that dificult, is it?
To use it, you just put it across the two front hobs of your gas cooker and turn them on so that the flame is just touching the base of the griddle. A bit of trial and error may be necessary, but you'll soon get it just right. Leave to heat up for a few minutes, oil the surface lightly with a brush and then put the chicken, sausages, egg, mushrooms or whatever on to cook. Wonderful!
So, my view is that Formbies are definitely not worth the money. Of course, others will appear here and claim they are the greatest thing since sliced bread!