Every night usually - there's been one every time I've been anyway. Yeah it was 1/2 NLHE - there was only one table open with a short waiting list but I've been before when there was 2 tables and a waiting list to get on them. There will definately be a lot more action on a weekend.
I ended up going quite late (maybe arrived just before 11pm so everything was well underway) as I was playing a tournament at the Maybury in Edinburgh beforehand. Their tourneys start registration at 7 and then play starts at half 8 so I imagine there would be a cash game kicking off around then - especially if there's no rake.
For Summer, the Alea's actually running cash games without any rake being taken 7-10pm Mondays-Fridays. They also have a jackpot thing running until Sunday where the highest ranked hand, using both hole cards, wins £1750 (i think). Prizes for 2nd and 3rd as well.
On Wednesday, quad jacks were 1st and I'm currently joint 2nd with quad 6s (K kicker but I don't know the other guy's kicker). Think 2nd was paying about £800. So hopefully I get a phone call on Monday morning about winning some more money