I might have misunderstood when you asked about gas fills. I assumed you meant something other than air. If it's just air you want there are loads of ScotSAC clubs around the area (see here https://www.scotsac.com/branches) and most, if not all, will have their own compressor. Pick an active one and join. Subs are usually very reasonable and you'll have buddies most/every weekend. Not much in the way of shops to buy air as already mentioned. Those in the west already listed, on the east side there's Edinburgh Dive Centre, Marine Quest at Eyemouth, and Rock House in St Abbs. Dive Bunker in Fife.
Believe it or not, bananas do contain a small quantity of Musa Sapientum bananadine, which is a mild, short-lasting psychedelic
South queensferry sub aqua club is very active, we have a couple of ribs, and five regularly. A great mix of divers from single cylinder through to plenty of rebreather divers. Send a message through Facebook, or email http://www.sqsac.co.uk/