Bednobs
Have you seen this explanation of COSOP? - which came from the Avon area but which seems to me the same business that you are tied up in.
http://www.avon.nhs.uk/transition/Your_Journey/Briefing_Sheets/COSOP_transfer_process.pdf
I've come across the Code of Practice before (in another Government department) but not heard it called this.
Reading it through, it looks like your key existing employment terms transfer across. HOWEVER you should be very clear to clarify what happens to your pension rights (which seem to be covered OK in this document) and the terms under which any future redundancy might occur.
I'll come back later to see if you have any questions about this.