According to Exemption 865 to the ANO 2009, if your JAR medical become temporarily suspended you can carry on exercising the privileges of an SSEA using a Medical Declaration form your GP.

You don't even need to apply for an NPPL until your SEP rating expires.

Anyone done this while waiting for a temporary problem to be sorted out ? Spoke to the CAA today and they asked me to send an e-mail. Which hasn't been responded to.

Yes I did it for a number of months following a TIA Stroke. My Doctor initially signed the declaration for 12 months for a class 1 DVLA Private Driving Standard ( Solo flying or with a safety pilot ) and when I had remained medically incident free and passed the usual Treadmill test to her satisfaction she signed me off on the declaration for Class 2 DVLA Professional Driving Standard ( taking non Pilot passengers ) The Declaration is due for renewal when I reach 65 years of age, which at the time was 5 years distant.

During this period of time I applied for and was granted the NPPL when my JAR SEP Licence expired. I have been flying my own aircraft since on the NPPL and the Medical Declaration.

It makes sense to me to be able to exercise the Privileges of the SEP Licence until it expires as the Doctors Declaration can impose limiting factors and you are also bound to NPPL conditions until such time as you can regain your JAR Medical.