Thats an odd one is that Ted.
That's because, as far as I can see from photos, it's not a Serley frame but std Honda F2 750 of that era. A Honda in a frock in other words.
I'm prepared to be wrong on this .... buuuut, Mr Seeley I don't recall manufacturing all the original Honda type frame junction and specifically the "gussets" used, which are presented on this bike.
As I understood it, he was commissioned to sell off final run of that 750 which was slow moving in UK market against newer design and stock.
I've got one here (not mine) original and bought from that dealer too ! Still in original ownership, to which I'm comparing. That one on a V plate.
They got the history of running Brabham (for Mr Eccleston) right, think it was way past tube frames at that point though, with more sheet monocoque arrangement.