A few random thoughts follow. (Please post again, with more specific requests, if you require further information):
The nearest ferry port (served from the UK) to Nice isn't even in France. It's Bilbao, in Spain. P&O sail from Portsmouth to Bilbao (but the route is being withdrawn in late September):
http://www.poferries....rtsmouth_-_bilbao.htm
However that still leaves you with a 625 mile drive. By far the best route planner, for European road travel is this one:
http://www.viamichelin.co.uk
By far the easiest way of getting from Cambridge to Nice, without flying, is by train. It would obviously require a bit of planning but you'd only need to get help across the road in London (from Kings Cross to St Pancras International, which is next door) and to arrange transport from Gare du Nord to Gare de Lyon in Paris.
For travel insurance, try here:
http://www.ch-travelcare.co.uk/
Chris