Cant seem to stop some brake squeal on one of the rear wheels. Every time i've had it in for a service the mechanics try something but haven't fixed it. It happens at low speed pulling up at lights. What causes this typically?

I had the same problem. Turns out the mechanic over tightened the handbrake nut.

I had the same problem. Turns out the mechanic over tightened the handbrake nut. did it squeal all the time, or only when brakingto a stop? Iget the squeal at low speed when pulling up.

Metal brake pads can squeal especially when cold. That probably doesn't explain why just one wheel squeals though. :)

I had this problem after adjusting the handbrake shoes. I solved it by setting them so that they 'just' spin freely with no contact then backing the adjuster off a few notches. Also chamfering the edges of the brake pads and putting some of that red anti-squeal goo that sets like rubber on them the squeeling stopped. I tied CRC anti-squeel aerosol that looks like grease and you put on the pad face and rotor surface, it only works for a little while. When I did the front brakes I used all new parts and it was good for a few months then started squeeling sometimes. Took the pads out, chamfered them and took the glaze of with emery paper. This solved it, now it hardly sqeeks at all.

Check that your pads still have the anti-squeal shims installed.
A lot of owners/mechanics chuck them out when they replace pads because they don't know what they are there for.