Let me answer this question in Zen master fashion by not answering this question.
I want to spend the weekend eating out, where's the best city in the UK?
London wins hands down in terms of diversity of cuisine and the quantity of options at various price points. Plus the Londoners are a fickle lot, any establishment that does not deliver quality will go out of business. Keep in mind that eating out in London actually requires you to be in London which has certain inconveniences.
Now apply the same logic to your predicament.
More direct answer: unless you're going to overdose on Cialis, a weekend is not that many punts. So you don't need the quantity of London or Manchester and any decent city will work out if you do some legwork. Think of a candidate city and then see what kind of reviews it gets here or on aw. Unless the punting is absolutely dire, and no I haven't been in Derby, you should be able to find a couple of girls to your liking.