As Spudqueen indicates, there are (very low) specificlimits on the import of tobacco products from non-EU countries (and from a few countries which have recently joined the EU).
The important thing to remember about importing cigarettes from (the majority of) EU countries is that they must be for personal use. Theoretically, you're allowed to bring in an unlimited quantity of tobacco products, as long as they comply with the 'personal use' rule. HMRC have introduced guidelines which suggest the maximum amounts you can normally import before they'll 'start asking questions'. However, that doesn't prevent them challenging people about whether tobacco products are really for personal use, even when the quantities are within those guidelines.
In particular, HMRC might well challenge someone who brings back several different brands of cigarettes. Equally, HMRC might be suspicious of someone who brings back both hand-rolling tobacco and cigarettes. (Most people either smoke 'proper' cigarettes or 'roll-ups'. It would look odd if you brought back both).
If HMRC believe that your tobacco imports are not for personal use (irrespective of the quantities involved), they'll confiscate the whole lot. If you want to convince them that everything is really for your own use, I suggest the following:
(i) only bring back one brand of cigarettes ;
(ii) only bring back one brand of hand-rolling tobacco ;
(iii) have an open packet of cigarettes (as the same brand as you're importing) in your pocket when you arrive ;
(iv) have a packet of Rizlas, and a well-worn hand-rolling machine, in another pocket.
Chris