Thanks. Research is what it is, and you have to do it, it's one thing having a preference in the absence of logistic considerations, its quite another it being the best option once logistics are overlaid. The timings of the flights being a major issue in this case. So far these things I do know
1. After arrival and checking into the hotel (even an airport hotel) it will be after 10.30pm. So "crash" is the operative word. It will be a bed and breakfast affair so clean and close are the only attributes that really matter.
2. Because the return flight does not depart until about 2130, we're going to have all of the final day to kill in Nice. This is why I'm thinking to head back the day before we leave, dump the car a day early and have a nice afternoon/evening in a nice 4/5 star in a good location. That way, even after check out, our luggage will not cause us a problem while we kill the best part of the day before flying
3. The rental (picking up day 2, dropping off day 6) will definitely be 5 days, HA rates for a 107 type being about £23/day which I am more than happy with. Probably about £29/day with maxed insurance. I'll give all your other suggestions a whirl to see if I can chop a few quid off, but I'd be surprised if there was much in it as these rates seem pretty good already. Lots of people seem to rave about Sixt just now, but when we went to Montenegro recently they didn't match HA's rates.
I was looking at the Mercure earlier, actually, it was on my list of possibles, so thanks for the validation. I'll look at the VF and BSM suggestions too (the commute into Nice is a quick and easy one so they're all in the catchment area for the last 1.5 days. I'll look at the annual waiver policy. This might be worthwhile as I probably hire a car about 25 days/year. I could put this through the business too as most of my hire is for business.
Edited: 11:07 am, June 19, 2013