Thanks ChooChooGuy. I'm looking at the reasons I opened a shop in the first place and trying to find viable alternatives, then I think I'll give it a try. I worked out that on the rare occasion I do sell something listed in SIF, after paying the higher rate of FVF I've only saved pennies, so taking the shop fees into account, I'm probably on a loser.
On the subject of other sites, I tried Ebid about a year ago, lured in by free listing fees, etc. I didn't sell anything at all. It seemed at the time that sellers were attracted by the low fees, but buyers hadn't yet discovered the site.