The barrel adjuster on my SRAM Apex rear mech has snapped, god knows how, but it has tonight on a ride.

A quick google doesnt come up with much for replacements, and £15 just for this tiny piece of metal and plastic!

Is this the sort of thing the LBS has in the back? Or am I realistically better off buying a new rear mech??

Well, there are at least 3 pieces of metal and one piece of plastic; pretty good value :).

It would seem you are not alone in your quest:

What exactly has snapped? http://www.bikeradar.com/forums/viewtopic.php?f=40004&t=12884835

otsdr – Thanks for the link.

Turns out it wasnt broken, its just a very odd cheap design, that means if the barrel adjuster is screwed out too far you cant really get it back in without taking the cable out.