so, he's v slowly getting better on the pulling front, but he's recently started barking and going mental if i leave him for a bit, anything i can do to stop this?
Separation anxiety....you've taken this dog on from being in a right state/stray haven't you? Now he doesn't want you to leave and is saying in dog speak 'come back and find me, I'm all alone'

Dogs are social creatures and would much rather they weren't left on their own, but life's not like that sometimes.
Is he chewing/being destructive as well? Does he pick up on when you're about to leave the house and start panting/licking his lips/whining, or not?
It is quite a common problem, I'd first of all make sure he was happy to settle down by himself and away from you. Does he lie on a bed while you get on with stuff around the house, or is he a constant follower? If he's following you all the time teach him to lie on a bed in another room while you get on with things. (teaching a settle
http://dogtime.com/dog-training-settle-down-dunbar.html here )
There's a couple of ways you can approach it from here on....
Build up the time in very small increments, so he doesn't have to be fearful when you go out (giving him something to chew or 'do' like a stuffed kong will help as chewing releases a happy chemical in the brain and calms dogs down). Go for 10 seconds, come back before any barking has started, then 20 seconds, then 30 seconds then 45, then a minute, then 2 minutes and so on, the key is to not let him get in that state where he's crying, whining etc.
The link below should be useful

Dogstardaily is a great site and was set up by Ian Dunbar who's really, really knows his shit. Legend
http://www.dogstardaily.com/training/separation-anxiety