Originally Posted by mrquattro
my floor measures 71cm wide and 143cm long plus there is a triangular bit that goes in front of this main floor section
I've just measured the "quick and dirty" floor that someone had made for my S100 and the equivalent three boards measure 86cm x 153cm. Plus the triangular board.
They are noticeably too loose in my boat so I reckon the three should be nearer 88cm x 160.
Considering the differences in transom, the lack of an access hole for a keel valve, and also that yours has two less attachments for the bow dodger than mine has, I'm now wondering if yours is something else, slightly smaller than an S100?
I'm certainly not an expert on old Avon boats though.
The S100 is 3.2m. If there was something which came in 3 or 3.1m that could easily account for your floor being at least 10cm shorter than mine.
It'd be interesting to hear from someone else with an original S100 or S250 floor for comparison.