Grinding on rear passenger wheels at slow speeds

[Jukie88]

Right noticed this morning as I set off for work that the rear left hand side is making a grinding sound !! It's ok at speed but when pulling upto a junction it makes a very bad grinding sound now as its dark I can't really investigate much more ive abandoned my drive to work so just wondering what I should look for ??

Something stuck in disc

Rear wheel bearing

Trailing arm bushes ??

Shock collapsed so wheel hits arch it's not touching ATM but car is very low at back so low infact I'm not sure wether its dropped any more :-(

Any help would be very much apreciated