I did a little bit of hunting around online on the issue of plaster. Thistle is apparently a brand name in the UK.
There are a variety of types of plaster available at the DIY and builder stores - and it sounds like the plaster available here in France has different qualities from that used in the UK. It may relate to the different building techniques used.
Your best bet might be to ask at a large building supply store like Leroy Merlin or Point P or even do some hunting around on their websites. From what I could find, the various types of plaster used here tend to dry much quicker than the UK standards, and it's important to get the right type for the right job.
Cheers,
Bev