You want to look for the cheap shitty cigars (in the US some of them are actually called 'blunts' right on the box), the ones where you know the cigar company is expecting you to fill it up with weed. If you go into a cigar store you're gonna get like a real cigar with good tobacco, and those are expensive (and a waste of a good cigar).
The cheaper ones are usually in gas stations and sometimes pharmacies.

I don't know what you've got in the UK but look for brands like Dutch Masters, Phillies, White Owl, Garcia y Vega. They usually cost around US$1 for 1 and $3 or $4 for a box of 5 or 6.