You could launch at calshot spit (near southampton) - it has excellent parking and a well maintained (RNLI use it) slip. You can play about in the solent, or head up the Medina at Cowes. Plenty of places to moor up on the medina (some in cowes, some further down). The folly inn is a bit further up the river, with its own pontoons for you to moor on and a water taxi. I think they have rooms too, but are likely to be popular so give them a call first.
Alternatively launch at lymington (quite tide dependent) and head to yarmouth - there are plenty of mooring sites in the harbour and you shouldnt struggle to find a B&B.
I've done day trips like this before which have been absolutely excellent, the folly is one of my favourite places to nip over to.