My parents were quite disappointed too. Personally I think a below average episode of the Royle Family is still better than a good episode of most sitcoms, so I enjoyed it, but you're right that some of the scenes were a bit silly (some of the cooking stuff - I found myself thinking 'even Denise wouldn't be that useless').
Maybe Nana's death should have been the end of it; especially when they couldn't get Ralf Little for this one.