A few of the alcoholics who would come in for frosty jack's or karpackie just went on or back to heroin, valium etc.

This seems an odd choice when the street value of Valium 10mg in Edinburgh is about £5 and will have a notable effect for a user for around 6-8 hours. A regular user will need much more than 10mg to maintain that effect.

Alternatively they could smash 22 units from Frosty Jacks 3L for just over £11 and have a better duration of action even when an established user.

It's just bad budgeting there. You should tell them when you see them and get those sales back in.