Since the electrician has changed the CU, issued an EIC, that is it. Your solicitor will advise accordingly.
If for the future you want to know what is Notifiable & Non-Notifiable under SI2006 go to the ODPM website and download it, or go buy the printed version (it's about =A316 so not cheap, but useful to whack ignorami over the head with).
Part P only came in after April 2005 - any work before that is exempt. Part P SI2006 permits various non-notifiable work and requires no paperwork for it. Full stop. Replacement, Maintenance, even if connected with special locations is non-notifiable. For example replacing an existing SWA across a garden (armour rotted/ cut, sheath damaged) or replacing a shower or replacing a faulty RCD or faulty RCBO (doesn't trip when button pressed).
This is stated in Black n White in the document, someone may have the link.