LOL, great question. And I feel duty-bound to provide a link without offering speculation. But I'm about to retire to bed and am still trying to get over some jetlag, so I'm not offering anything quite specific. Take a look around this FAQ:
HM Revenue & Customs Travel FAQs
If your question's not answered there, look around the site in other areas.
I would venture to say that Milk Duds would not be restricted if for your own use, but you'd have to pay VAT on anything in excess of...sorry, forgot. Cigarettes, likewise. BUT, that's the rules for people living in the UK and bring from another EU nation, which is probably not what you're asking.
I *think* for coming to the UK from a non-EU country, you are limited to 2 cartons of cigarettes, but I don't think the Milk Duds are restricted, but you may have to declare them if they go over a certain monetary amount.