After seeing the harvester deal, which is a great deal in itself, I mentioned in the comments that Premier Inn also do an all you can eat breakfast for £8.75 including drinks. If you have 2 kids or more this will work out cheaper with drinks included. You pay £8.75 and up to two under-16s eat breakfast for free when one adult orders a full Premier Inn Breakfast. This is the cooked breakfast and includes unlimited coffee and juices.
There is also the Continental Breakfast at £6.25
Not every premier Inn are the same though as they use other chains to supply the food eg Brewers Fayre, Beefeater, TableTable etc. Due to this some do not supply a buffet style breakfast ,so if you prefer this check before visiting. I have done both ways of buffet and also cooked to order but don't hold back if you have to do the cooked to order, it's your money.
I think a lot of the chain pubs like TableTable don't mention this deal on their website because it's done through premier Inn and not every chain pub will do it, so worth asking your local Premier Inn.