After a lot of thought, procrastination, research and too many late night "scrap it and start agains", I have decided to go with a downloadable PDF portfolio.
I approached the design with one foot in the 'old school' and one sort of in the 'new school'. The layout is A3 with images compressed to 150 dpi which means it can be printed with OK quality, if needs be, which meats the old school requirement.
The new school is bit more challenging and in the end I settled for a PDF document which can be downloaded and viewed with relative ease on a PC, phone or an tablet. The A3 landscape layout works quite nicely on an tablet with each page a swipe away. I figured that was most likely how I would look to present it or refer to it in an interview.