Bristol Channel is a bit limited on slips and is 100% Tidal dependent.
I've used Options like Minhead Harbour Watchet Harbour... Portishead ...Bristol Marina Burnham and they all work for Getting to decent Fishing Marks.
...Timeings and windows all depend on prevailing weather and tides...BUT.. and its a big BUT for a smallish Honwave.
You must always take into account the very strong tidal flows and almost Otherworldly currents you can and will most certainly encounter ..The Bristol Channel is in my experience like nowhere else!
..All fishing is from an anchored Boat with Up-tideing being the most favoured method as you probably know...(BIG Worm/cocktail Baits)
When a Spring Tide ( a good time to fish) makes and there is any sort of chop/wind it can be quite a strain Anchored up for smallish inflatable...(and Crew) believe me I know from experience
It can be done,but you do need to pick a good weather window,and a decent Rig you can rely on.
IMO in a smallish vessel like yours it's best done with another Boat too.
The Harbourmaster at Watchet and the small tackle shop on Minehead Harbour "West Coast Tackel" are both a good source of local and up to date info/knowledge