Believe the rules have recently changed (infact I think EASA had the rule change a while the UK CAA has only recently implemented). So they can only grant the IR validity if you have a relevant class rating on which to exercise the privileges.
https://www.caa.co.uk/Commercial-ind...or-aeroplanes/
Believe the alternate rule still applies, if your last IR was in the aircraft the next re-validation can be in the FNPT 11. As long as your MEP is current then the examiner can still then extend the validity of the SPA ME/IR /SE. However if you revalidate in an FNPT 11 and only have an SEP but no MEP, I believe the examiner could only extend the validity as a SPA SE/IR.
However you do have the option of renewing (assuming if you don't have an MEP you have gone past the expiry date so it is a renewal) the MEP at the same time as the revalidation or renewal of the SPA ME/IR, but that would have to be done in the aircraft.