Pre tdi pistons 41mm, just measured one. But as others say only way to be sure is to measure yourself. Just taking a pad out should be enough to do the measure I recon.
Yup, the different sizes used are so different that it's hard to make a mistake - 41 versus 46 mm - even just guesstimating with a ruler with the brakes still on the car.
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.