I've cracked it (UK English expression for it works)
For whatever reason it didn't like CCC. I had to make a bootable mavericks drive on a usb stick using Diskmaker X (Freeware but accepts donations).
Then I could partition and install via the mavericks installer, then use migration assistant to get all my old data. HOWEVER...... the original mac book pro disk cannot now be read by the machine in a caddy????, so I used the back up I'd made before all this debacle started.
It is so important to have a copy of the original hard drive before you attempt this!!!!!
Interestingly also the SATA negotiation speed has gone from 3 to 6Gb, (all the firmware was up to date)
So a huge thank you to everyone who took the time to reply to my post, and hopefully anyone reading this with similar problems won't now waste 2 days trying to get the Seagate XT 750 working
All the best
I put my old laptop drive in running Mavericks and made a USB pen drive bootable version of Mavericks using Diskmaker X. I used this as the startup disc.
I swapped out the original drive for the Momentus and ran the Mavericks installer which partitioned/formatted the Seagate and installed Mavericks onto this then used migration assistant from a cloned drive.
The original drive can't be seen now but the cloned one can in a firewire caddy. I think it's a SATA issue, my mbp now has a 6gb negotiated speed. It's like a new machine now, I'm very pleased I persevered