My dealer says it's based on the GP platform, as do all the reviews.
I sat in the Dynamic today and it is fantastic. Very easy to find a perfect seating position, and lots of space for my clutch foot. A rubber floor too, which is sensible. Great visibility because of narrow pillars. Also, well chosen plastics and clever design means it feels smart rather than cheap, in fact it is rather elegant inside. Great storage too. It also has hydraulic power steering, which means better feel than the electric set-ups, and the reviews say it is very supple and quiet on the road. Now, when they fit the 1.6 Diesel, as I hope they will, I will probably get one. The salesman did say there was a 90bhp 1.3 Diesel on the way. Do I sound enthusiastic? That's because I am.