Okay then, my Carradice Barley has arrived. My first impressions were "wow, it's a bit bigger than I thought", and "wow, it was handmade by Patricia!". Seriously it is handwritten in biro on the inside label.
I've attached it via the saddle loops, and the seat post. I've managed to get a mini pump, couple of bungee cords, long fingered gloves, waterproof trousers, overshoes and skull cap in the main compartment. The water bottle went in there too, mainly to see if I could get my lunch in there. Pretty certain it can, and I think I can get a waterproof jacket in there too.
In the two pockets at the side went my clip on lights, tyre levers, multi tool and p*ncture repair kit. Oh, and spare batteries.
It will be a faff for taking on and off though. I just leave the pannier on the bike and take out my lunch when I get to work (secure area). So it won't bother me, but if you have to take it off everytime then one of the quick release options are a must. I mean an opportunistic thief won't be interested in it as they'd have to open the bag and try and unbuckle it to get it off. Not a quick job, and I doubt your bog standard chav would know how one is secured to the bike. Somebody looking to steal one to "order" will probably have off with it though.
So pretty much can get what I want into it. It does look huge on the bike though. I'm hoping it won't hit the back of my legs as it overlaps either side of the saddle by a few inches.
Overall impressions are very good. I'm quite pleased. Something smaller might be more suitable if you just wanted to carry tools though.
Not tested out the waterproofness of it yet obviously, but it looks the bizz. Not sure about the side pockets though, they don't look very secure.