Re-Registering in the UK
 

I am currently operating a motor glider in the UK with a German registration, and plan to re-register to the UK next month. It holds a valid C of A, and the ARC runs out early next year.
I have the LBA form for de-registration, and the CAA form CA1.
I understand that along with form CA1, I have to send a copy of the C of A, noise cert and ARC to the CAA, whilst the originals are sent back to the LBA.
Question is, do I send both forms out at once, before I fly the aircraft to the mtce organisation to re-placard etc, and what sort of timescale am I looking at. Also, what is the likely- hood of the CAA wanting to audit the aircraft? ( Cost implication )
Thanks
Ian K