I have to admit, I'm not as sold on this being a great place as I was before I bought the thing ! I live near Thornbury, so really close to motorways and extremely easy to get to most places. I thought 'there are loads of brilliant launch sites within an hour or 2, and some really special ones within 3/4 hours'.
The 3 to 4 hour ones (Saundersfoot, Dale, Solent) are well worth it and if you've got a whole weekend or longer definitely make the summer. The 1-2 hours haven't been as plentiful as I'd have liked but that may well be because I faff too much.
I've not been brave enough to launch into the muddy bits as pretty much every warm weekend there's another news story about some fool getting killed or nearly killed, which is a bit off putting. I've met people who are in the coastguard at Weston & Burnham and it would just be embarrassing to have to be rescued by them if I made a slight miscalculation, so I haven't really tried to explore places like that. Maybe I'm missing out, or maybe I'm being sensible - I don't really know.
Portishead is expensive, and Bristol docks is fine for a potter around but the Merc won't cope with pottering so that's off the menu, but you may be ok with either of those.
There may be a bargain scruffy looking SR4 up for sale if I find a really good deal on something slightly bigger which I can dry stack at Cardiff, as I'm finding most of my playing out is done around there anyway! I'd offer you a go but not sure when I'm next free other than the Falmouth trip and you'll probably have bought something by then anyway.
Having said that, now I've started on the slippery slope I don't think I'd want to spend a summer without a boat, when things do go right it's so much fun.
Best of luck with finding the right one.