Very simple. This is all that I wrote them:
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Civil Aviation Authority
Personell Licensing Department
Aviation House,
Gatwick Airport South,
West Sussex RH6 0YR
United Kingdom
<place>, <date>
Dear Sir, Madam,
I hereby wish to apply for the JAR-FCL Private Pilot License (Aeroplanes).
Please find enclosed the following:
1.JAR-FCL Private Pilot License (Aeroplanes) Application (CAA form SRG\1105)
2.Flight Radio Telephony Operator's Licence Application (CAA form SRG\1106)
3.JAR-FCL PPL(A) Skills test report form (CAA form SRG\1166)
4.Original JAA Medical Certificate, class II, number XXX
5.Original FAA Medical Certificate 3rd class and student pilot certificate
6.Copy of my passport, certified by the head of training of XXX
7.Copy of my PPL(A) Qualifying Cross Country Certificate
8.Original JAA logbook
With kind regards,
<my personal details>
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Item 5 was eclosed because I did my PPL in Florida. A UK-trained PPL would not have one.
Got my license, plus all the originals, back in about three weeks (as far as I remember).