I've attached the size matrix for the Raven Sport Tour, from the Raven Tour brochure Issue 7a- Jan 2012.
But this brochure has no recommendations for height of rider.
I am about 6 foot/183 cms tall and have a Raven Sport Tour in the 611S largest size. Theoretically a bit too big for me, but in practice the fit seems OK. I have quite a lot of seatpost showing, no problems with standover height or reach to the handlebars. A 586S would also have been OK for me, a 561S would have been a bit small, but quite rideable with a longer stem.
I also have two Raven Tour bikes, sizes 587S (size recommended for me by Thorn Cycles) and 612S. Both these sizes fit me OK, but the higher standover height on the 612S would make it slightly less suitable for off-road riding with the 2.0" tyres I have on it. As my 612S is set up as a utility bike for local errands, this isn't a problem for me.
I'm quite fussy about saddle height and reach, but with "old fashioned" road/touring bike sizes I was quite happy with frames measuring 22" to 25 1/2" (56-65 cms) so long as I could get the right length stem and seatpost.
As JimK says, Thorn use "virtual seat tube" heights rather than the old fashioned frame size. Raven Tour, Raven Sport Tour and Nomad all have sloping top tubes, so lower standover heights than the equivalent non-sloped frame.
Comparing my 2 Raven Tours, for the same handlebar reach, as the 612S frame is longer it requires a shorter stem than the 587S, so frame length is probably at least as important as height.
If trying to work out rider heights from current Thorn models, as the geometry of the Raven Sport Tour is fairly similar to the Raven I would use that as a guide rather than the Nomad.
