Many touring (and road) bikes now have some degree of a slope to the top tube making seat tube length relatively meaningless for sizing. A sloped TT will result from either a taller HT or a shorter ST. If the ST has been shortened to produce the slope then that dimension is no longer a constant that can be used for frame fitting. Looks like the Windsor Tourist may have a slightly sloping top tube which may vary from size to size, thus you cannot compare it's ST "size" with any previous bike you've had with a level or different slope of TT. Hard to compare with the LHT also as they have fairly level TTs.

For example, my road bike has a 51cm ST (center to top) and a level TT. My touring bike has a 43cm ST and a steeply sloping TT. Both have short head tubes (TT and DT touching). Each has the same "saddle/pedal start" height (pedal axle to saddle top) of about 83cm. The touring frame just accomplishes this with more seat post exposed. I appreciate the higher standover. The road frame has more of it's "saddle/pedal start" in the seat tube with less exposed seat post. ETT of 53-54cm is close to identical on each frame...





For the three choices that you have posted I would choose the one that gives you the desired amount of exposed seat post relative to your "saddle/pedal start". Yes, being a mail order bike this may be hard to envision. You could always measure your start height on your present bike (crank in line with ST), then subtract the three Windsor ST lengths to see how much post would be exposed with each choice. This of course is assuming all bikes have the same crank length. You also might want to compare the 3 choices of "standover height" (758, 792, 812) with some sort of home made measuring jig.

My head tube is just 75mm. With an old style quill stem riser the bars will reach 2" higher than the saddle. Saddle rails are 8" above TT...