Two CUs, both main switch with all RCBOs. One for usual circuits, the other for off peak storage heaters.
Storage heaters being removed, so the RCBOs in the off peak CU were moved into the other CU, and the circuit cables reconnected. The cables were not shortened/lengthened or changed in any way, the same RCBOs were used. The DP switches at the ends of the circuits were changed to single socket outlets. ....... New circuits or not?
Common sense says no (not new circuits) - changing storage heaters to sockets, per se, would certainly not (in my book) make them 'new circuits'.
In terms of regs, who knows. If one takes the regs literally, and given that you say that you used the same RCBOs (as in the other CU), they would still seem to be the same 'circuits' that they always were (i.e. not 'new circuits'). I suppose there might be more (IMO silly!) room for argument if you used new/different RCBOs - but that would be daft, since it would imply that replacing an MCB or RCBO would constitute 'installing a new circuit' - which it clearly isn't!!
IMO, a case for allowing common sense to prevail!
Kind Regards, John