I think £15 per plate for good food in an independent pub is about right, or £25 in a good restaurant plus drinks. Mind you it is classed as a treat for us, say once a month

Personally I wouldn't entertain eating in a chain owned place like Harvester, Weatherspoons ,Toby Carvery etc.
it certainly is a lot more expensive down here seeing all your replies...but cleggy why not weatherspoons etc never ate in any you mention although this time last year i spent most if my time in premier inn(due too work) and due to that was forced to eat 90 % of the time at a table table...which did seem good value... 
Nothing wrong with the places, but they are all the same, it's just that when I eat out I want something different cooked by a chef with seasonal local produce and a changing menu. A few near us put up a chalk board of the days choices freshly cooked and as they run out are removed from the menu, and replaced with something different.

I often wonder what happened to proper pub grub, Cottage Pie, chips & beans, Pie and mash, Ham, Eggs & Chips, Pie & Mushy peas, when food was only served at lunchtimes and cheap. Good honest grub with a couple of pints in the local they are all mini restaurants now and lets kids in, even women