To follow up... After chatting to a couple of members, It seemed like the only logical place and person to go see was Zane at Automatic Transmission Repairs in Plimmerton. He's a certified ZF whizz and covered to do MBI work also. Pretty much everything was replaced bar the drums. This included a split valve block, all bearings, clutch packs, pistons, pressure regulator valves etc etc, The list goes on...
Zane really knows his stuff and takes the time to answer questions. Having been here before with an L322 Range Rover with the same m62tu and ZF 5hp 24 box, it was reassuring!
It took a few weeks because the job was as big as it could have been and a bunch of parts and overhaul kits had to come from overseas.
He didn't disappoint and i now have my car back running better than ever.
Any gearbox woes? Go see Zane at Automatic Transmission repairs in Plimmerton