I'm sure others will elaborate, but since I'm slowly hour-building too, heres how I know it.
Hour building that counts toward the 100 hour P1 requirement for CPL licence issue must be on what were known as Group A aircraft - over 450kg all up weight and on a CAA or EASA CofA, or on a PFA Permit to Fly.
As far as I know you can get a 3 axis microlight rating (ie, under 450kg AUW) added to your JAR PPL to fly these A/C, but you cant log it toward CPL issue.
The Aircraft you mention - the robin should be fine. The Eurostar (I'd love to fly one) only if on a Permit.
Good luck. I'm currently flying a club 152... would love to be part of a group but the finances dont stretch that far!
