Trying out saddles in the UK I've been on the lookout for a new saddle recently and everywhere I look on the web it suggests you should try lots of saddles before you buy.

I went for a professional bike fit, which was great but the guy didn't have many saddles to try. My local bike shop(s) don't offer a try/buy service.

Is there any saddle swap/service available in the UK that will allow me to try some saddles? I contacted Wiggle (popular online bike store) and asked if I could return a saddle if it didn't work out - they said no as the rails will get marked.

What should I do? Just buy and ebay?
I'm not sure about UK-specific swap service, but here are a couple of things you can try: 


Check with your local bike shops and see if they have loaner saddles. My fave local bike shop has loaners of almost every saddle they carry and a sign out ledger. You can sign out the saddle and leave your credit card info. If it's not returned within a couple weeks, they bill you for the full price.
Buy a saddle you're interested in, and carefully wrap a long strip of electrical tape around the saddle rails. The rails are thing enough that the width of the tape can pretty much go around. Then clamp them just firm enough to stay in place, and you'll find that after removing the tape, there are no marks. Voila, you can return it according to the return policy of most shops ("no marks on rails"). If the saddle comes zip-tied into a cardboard backing or box, just buy some dollar store zip ties of the same color to put it back in. I've done this with great success. Just make sure not to lean it against a brick wall or ride in your retro 70s punk studded leather bike shorts. 
Check your local bike forums/ club scene and see if anyone is willing to loan out a saddle you're interested in for a few days/ weeks (offer them a safety deposit).