Thanks for all the useful (and not so useful) answers.
Having dabbled in tri, I was pretty sure that the people at Slowtwit kinda claimed the honours behind stack and reach, and it’s promoted massively in TT/tri bike sizing… I also realise that it is just a useful way of comparing frames, not everything I need to know.
The annoying thing is that the bike I quite fancy is a Kinesis which doesn’t seem to be easy to throw a leg over in shop (Kinesis have no 60cm in their demo fleet at all apparently), and my LBS is rather limited on brands… I guess the next thing is to see who on here will lend me a 60cm Pro6 and a 58&61cm Caadx to compare.
Had never really measured the Giant before – reckon it’s at least a 60cm seat tube if measuring to an imaginary horizontal top tube. Why did they label them as 58.5cm?!
I am looking mainly at all purpose/CX/Gravel bikes and most seem to top out at 60cm frames… I guess it’s time to call all the not local shops to see who has a 60cm+ bike I can run a tape measure over/test ride. I also realise that a CX/gravel bike prob wont be as stretched as a full on road bike.
Just remembered I hired a bike on holiday last year, a 60cm Emonda and that seemed a decent fit. Off to google the geo now…