I've seen this boat a few times while it's been ashore in Emsworth for the winter and spotted someone working on her from the other side of the mill pond. Sadly by the time we'd walked around there was no one about so no details unless folks with local knowledge can help.
I'd guess at around 18 feet, GRP construction with hard chine and shallow dead rise. Up front a useful cuddy.
Someone had been around and taken the cover off to reveal a spacious and useful cockpit with a good storage space forward.
A nice handy boat of pottering around the harbour, a bit of fishing or a trip over to East Head of a picnic and a swim, when the weather improved of course.
While I was wondering about the design I came across this John Westrell designed Allegro which looks mighty similar, but I'm happy to being corrected.