I have obtained a few more details. The first 20 or so hours of training were through Oxford Aviation as part of their ATPL programme. The training took place in Arizona in 2007. The training was apparently following the FAA PPL syllabus The remaining US training took place at different school, not apparently affiliated to any European organisation and again following the FAA PPL syllabus.
I have contacted both organisations and asked them if their training was toward the JAA or FAA PPL, and if any of the instructors were dual qualified.
Am I correct to assume that instruction given by a US instructor not qualified as a JAA instructor cannot be credited toward the EASA PPL ? FCL035 does not seem helpful in this respect.