Thanks very much for all the comments chaps. I've now bled both rears with the 750ml of fluid I had left, there were plenty of bubbles and this has partially solved the issue. Will buy some more and do the fronts tonight. The handbrake is attached at both caliper ends and is "pulling" properly on both sides when i tighten it. However, only the passenger side is actually working so I assume this is something going wrong in the caliper as when I have the foot brake depressed it locks both rears fine.
Also managed to get the cap off the hub having purchased a stonemasons chisel, lol. Not teaching me to suck eggs at all Mentalpen as I've not done this before, only pad changes on the front of 206 GTi and fluid changes, so this has been a learning curve!