my RT examiner (and I) were not aware that the CAA requires not just the oral but also the written exam if you pass your RT in an ICAO country
Any RT Examiner should be aware that they cannot conduct the RT Practical test unless you have already passed the written exam! Either the UK National written exam or the JAA/EASA Subject 90 written.
CAA Standards Doc 2 NOTES FOR GUIDANCE OF AUTHORISED RTF EXAMINERS
4. WRITTEN EXAMINATIONS
The written examination paper(s) are to be completed before commencing the practical test.
Where did you take the practical test, and why did you not do the written paper the same time? The examiner's instructions are quite clear and the written results have to be entered on the test report form? The UK do not accept RT practical tests conducted by Examiners they have not appointed.