Hi Ian, our leaflets are different, A4 folded to DL. We recently found someone who was 2/3 the price of our previous supplier. I thought that was a bit dangerous, so I spoke to them at length about why they were so cheap.
Basically there are different capacities of machines, so if you find someone who is setup for big runs in a particular format you may get a very pleasant surprise on the price. So, someone like you coming to my printers for your A5 double sided would get a poor price (they are set up in a big way for my style of leaflet).
The guy said the key is to call round until you find someone. If you're ordering a decent run, don't worry about finding a local company - we used to get ours from Warwick (112 miles away); delivery is pretty trivial compared to finding the right printers.
The other thing that's got us out of hot water a few times is that I pay bills on the day they arrive (often before the printer's even dispatched the goods). That means that when I've had to call at short notice, they are keen to do our work first (printers suffer bad cashflow as much as most people).
Hope that helps,
Vin