The road to Dartside is a narrow, but that's Devon for you. I've used it for years with no real problem - just take it steady. Dartside is OK c. 2.5 hrs either side of HW, but if tides are not favourable Brixham slip is only a 15 min tow.
If you don't like that Dainton at Yalberton do storage, but you'll need to tow to launch every time. Not sure on prices but I think it's c. £4-5 /m/ week.
Ribraff might have some room in Dartmouth if you drop him a pm, but parking will be an issue.
If you're down for a couple of days you can always berth over night at one of the marinas - Noss, Darthaven, Dart Marina and recover on the next suitable tide.
Member of the Macmillan Round the Isle of Wight Club