Hi NJJ, I don't know this car specifically but I do own an Exige S roadster. You're right, they are in a slightly strange position in the S3 line-up - I wanted an Exige V6, having previously owned an Elise, but I knew I was rarely (if ever) going to track my car. And I'm a big fan of touring in Europe / Scotland etc. The roadster was therefore perfect for me - it has a slightly more compliant suspension set up than the coupe and misses the aero - splitter and wing. Otherwise it's the same car for a fair bit less money. (And looks better imo without the rear wing).
I think this Stratton one may be slightly overpriced. Mine is a 2016 model (it overlapped with the beginning of the 350 Sport production) and had 11,000 miles when I bought it about a year ago, and I paid less than this Stratton car is advertised for, although it is IPS, not manual. But even discounting the IPS in my car, I think Stratton's car is still a couple of grand too expensive. Have you spoken to them and seen what they can do price wise? The blue / tan combination is lovely, probably the best colour combo.
Also in case you haven't seen it, Rory Reid did a review of the Exige S roadster in exactly the same colour...