I managed to get an hour at Edinburgh Bike Co-op in Manchester on Saturday and found the following...
Whyte Dorset - Fantastic, found it quick and comfortable (as opposed to most of the cross/audax road bikes which I felt too upright on), however I tried the 'S' which was a tiny bit short on the toptube/stem.
Whyte Suffolk - this time in a medium, and found it slightly too long. Also, I don't know if I was imagining it, but it didn't feel quite as quick as the Dorset (the frame is the same so if there is a difference it could only be down to size). But the brakes were very, very good (they're the TRP HyRD cable operated hydraulic brakes) which is unfortunate as I'd hoped it wouldn't be noticeable and I would be happy with the cheaper model!
Whyte Charing Cross 2013 - Again this felt like the other Whytes (very nice), but as a 2013 model there is very limited availability.
Giant Revolt - this felt quick and comfortable, but very upright to ride...
EBC Revolution Cross Pro - this just felt very sluggish.
So, its looking like unless the Giant TCX SLR 2 wows me then I'll be trying to decide between Whytes and trying to find a Whyte dealer that does a 'proper' bike fit as I seem to be somewhere between sizes...