Thanks,
I managed to find both Brian McDermott's book for modellers on the S&DJR and the OPC trackplans.
Whilst the S&DJR is a worthwhile proposition in 4mm, the lack of a decent* S&DJR 7F prevents any further consideration.
Tim
*The resin versions look appalling as does the DJH kit, unfortunately the new owners of AGM seem to have no ability to produce updated versions of the Alan Gibson Models kit.