I have read the good and the (lot!) of bad about J17 - but in my eyes though I'm just after a car, not aftersales or warrantys etc, so would treat it with the same risk as a private seller. If in fact the roof (in this case) was broken and they didn't fix it, I would never buy the car. 
  
Funnily enough I was also looking at the first car AMT linked to as they are roughly the same distance from me as J17 are, but I do have my heart set on a black zed. I'm in no rush though and have a relatively high budget, so will keep looking! 
  
What is the tax difference between the pre- and post-facelifts then? 
 
So you just want the car....and I am sure you expect a decent car for your money, with no issues, even small ones. 
So listen to us and avoid unless you want grief, no matter how small. 
  
Plus it's advertised as a GT, there are some buttons missing on the steering wheel to prove that it is a GT