At the risk of opening a can of worms ...
I am sure you will be able to find all sorts of ways to measure your body and determine the perfect theoretical top tube length, but unless your torso and arms are extremely long or short in relation to your inseam, you'll be able to make do with whatever comes with the seat tube in your size.
Depending on whether you want to be more stretched out or more upright, playing with different bar stem lengths should enable you to find a fit that works for you on most bikes.
The Dawes Galaxy was made for touring, so I would want comfort to take precedence over other requirements. In my case - I am not particularly flexible anymore - that means a limited saddle-to-bar drop, so my touring frames are all close to the upper limit of my size range.
I just measured my own Galaxy (a bare frame from the early eighties that I haven't built up yet) and it has a 64.5cm (25 1/2 inch?) seat tube (center-to-top) and a 58cm top tube (center-to-center). That should work well for me.
My inseam, BTW, is 89cm/35" and this Roy Thame is very comfy. It is a 64cm frame, with also a 58cm top tube: