Thank you Graham, that is much appreciated.
The boat is from 2007 apparently, so would probably suffer from all the initial weaknesses.
I build wooden boats (for fun, not professionally) and I was a bit - let's say surprised, when I saw all the screws going into the bare GRP to be honest. Especially in the structural bits at the chainplates and the tabernacle area I would not have thought I'd get away with this on my boats without reinforcements.
I don't know how much of this stuff is original and how much is later maintenance - I can't imagine those really long screws sticking into the gunnel compartment are original.
I'm not thrilled by the state of the boat - the sails are also 15 years old and I'm sure they must be quite tired after that time (given how little care the rest of the boat has gotten).
I would do the modifications to the ballast tank you mentioned and add a bilge pump. The seating I'd replace with marine cork or something. Most hatches need replacing and the seal around the outside of the seats.
And I'd strip, fair, sand and repaint the bottom, CB and rudder, perhaps the topsides as well, which would give me a chance to add some bedding compound to the rubstrakes and reduce leakage through those screw holes.
I don't mind putting in a bit of work, it's more the structural bits you mentioned that I am worried, like the CB pivot area (which I don't think is reinforced with stainless steel - so that's something I'd have to do if I can), the mast tabernacle and that chainplate repair job. I don't know how much I can trust these areas.
It seems those first generation boats were not built to a very high standard and have their share of issues, but are priced with the current value of a new latest generation build in mind.
This one is offered at 13k - inc. the Bramber trailer (I don't know if those are any better than the originals) and there's a newish Mariner 3.5hp.
Needing a new set of sails and all those repairs (some of which I think are safety issues) I'd expect I have to spend at least another 5k and a couple of months in the dock to get her into shape.
For that kind of budget I can get a newly restored folk boat with new sails, trailer and electric drive system and still have some change left - or a Beneteau First 211 in top condition.
(Completely different story, but you could even get an IOD yacht for half that price - that seems crazy).