As he now has a ICAO compliment PPL
Does it actually state that on the licence?
Could he just do a SEP class rating course at an ATO/RTF plus test and then add a SEP rating to his PPL.
According to Article 65
65 (2) The CAA may include in any United Kingdom licence or National Private Pilot’s Licence (Aeroplanes) any rating specified in Section 2 of Part B of Schedule 7.
The SEP Class Rating is not specified in Schedule 7.