Fairly recently received from UK CAA:
Thank you for your email received - please accept our
apologies for the delay in replying to you.
In order to regrade your expired ATPL to an EASA PPL, you
are required to:
• Submit application form SRG1190, along with the fee of
£72.00.
• Hold a current a valid Class 1 or Class 2 medical
certificate issued by the UK CAA.
• Current and valid English language proficiency as per
CAP 804, Part I, Section 4, Part M – ‘Privileges’. To
exercise the privileges of a Flight Radiotelephony
Operators Licence (FRTOL) the holder must have
English language proficiency Level 6, or non-expired
English language proficiency at Level 4 or 5.
You are not required to hold a current rating in order to
regrade the ATPL to a PPL, but you will not be able to
exercise any privileges. If you wish to renew your SEP, then
you will need to attend at ATO, who will provide discretional
training in order to ensure you are at the standard to regain
currency. Once any refresher training has been completed,
you can apply to have the SEP put back on to the licence by
submitting:
• Application form SRG1119C
• Course Completion Certificate for the SEP refresher
training
• Examiner report form SRG1157
• Fee of £88.00
This can be applied for at the same time as the PPL regrade.
Our current turnaround times for this type of application is 10
working days.
Kind Regards,
I'd guess if you want to do SEP flying on your current ATPL, just do the second half of the procedure.