quite pleasedHad a letter through from their head office this morning saying (roughly) that what I had was a standard serving, that they're sorry I didn't enjoy my experience there, and would a £5 voucher convince me to carry on spending my money with them?
Result!
I still think they serve stingy portions, and I wouldn't order that dish again, but I am impressed by their swift reply, and by the fact that they immediately offered recompense. The restaurant concerned is so local that it would be a shame to cross it off the list completely, so I'm pleased with the way things turned out.