I had missed the line in Article 1 of Regulation 290/2012 that amended the final replacement date in Article 4 of Regulation 1178/2011 from 2017 to 2018.
That was sneaked in when it was obvious that no-one else (apart from the UK) was going to be ready to issue part-FCL licences until Apr 2013, so Apr 2018 was the last valid date for a 5-year licence issued immediately prior to the EASA changeover date.
Incidentally, a non-JAR compliant pilot licence may still be used for flying EASA aeroplanes after Apr 2014, but
only within the scope of the LAPL(A) and
only until Apr 2015.
The CAA has already had to come up with 2 x 2 month deferments regarding Flight Examiners (1 refers to seminar requirements, the other to non-UK Flight Examiner briefing) - are we
really sure that there won't be other issues too - such as the situation regarding PPL exams / mandatory 'groundschool'?