As robin has stated the adhesive is 3M 467MP which is a very very stable product. We have used it to stick elevations onto our architectural models for years now and never had any problems with it peeling off, even when the model is in constant bright light and heat. As long as you give the tiles a good firm push to seat them properly they will last for a very long time!
I had to remove some from the roof of a model we did 6 months ago and I had to resort to using a chisel and a shocking amount of lighter fluid! They came off eventualy but not with out a fight!
The sand house is looking fantastic Robin, I am just cutting the glazing for the roof of the main shed and the workshop, so it will be complete today! I will email you a picture of the shed and workshops as I have taped them together to check it all still fits.
Looking forward to seeing you and your models at Watford.
cheers
Chris Dening
york modelmaking