right after taking back a whole wall to take off all the loos plaster it is now back to bare brick and very lose morter......... should i put a thin layer of concrete on to fill inbetwween the bricks befor a use thistle hardwall

remove anything that is loose and just get the hardwall on the wall
No need to pva

going to take some photos over the weekend i am more worried that the wall needs strengthening as so much old lime morter is crumbly and missing

Why dont you float the wall with s&c. It will fill in the missing mortar and float the wall at the same time!!

Also i prefer to use s&c cos its cheaper!!

what mix would i use for this?

5-1 with a bit of waterproofer. Thats what i use anyway

i was going to level out the wall using the bonds sytem how thick should the wood bonds be?