Why is my 2006 BF MKII XR6 making a clicking sound?

I have 2006 BF MKII XR6 that has been regularly serviced and well maintained. About a week ago it developed a strange clicking sound from the rear driver side wheel. It sounds like a low level intermittent grating noise from inside the car that increases/decreases with speed. At first it was only in Drive then started to do it in reverse. The sound seems more noticeable with deceleration and is sometimes not even there with acceleration. It also seems to disappear when braking.

I've had my mechanic look at it and he says it's not the diff or the wheel bearings as it doesn't whine or growl and it comes and goes but he cannot say what it might be. He actually said "I can't see any major issues with it just drive it you'll be fine. If it gets worse bring it back". 
 
 My hand brake also recently failed (yet to be fixed) and it seems the driver’s side cannot hold pressure and the cable is loose (won’t hold adjustment) making the actuator arm rattle a bit. I have bought new park-brake shoes and tried to replace them (starting with the driver side as it was the one at fault) but could not get the rotor off and gave up. I think I may have adjusted the shoes up instead of down and kind of hoping this is the cause of the noise. What could be the source of the noise?