Thanks for all your replies guys...but it's just a shame that as usual the bitchiness on this website over-rules simple, clear advice!
Having spoken to the CAA to clarify the confusion this has all caused - I have to send of my license for renewal with appropriate fee, then go and renew my SEP rating, by doing a less complex Skills Test (1.5-2 hours max inc. oral theoretical exam) and then I can send off the paperwork for my full PPL(A) renewal (once I have passed, obviously!).
Thanks,
Sam