Leekie, I'm in Wolfwil, between Olten and Langenthal on the river Aare. We used to live in Oberwil, Zug a few years ago, so know Zug quite well.
As far as the dahlias are concerned, next time you plant some it might be an idea to put some chicken wire underneath them, I reckon the roots would grow through the holes with no problem.
Good luck with the rest of the dahlias!
Ahh small world eh?! Thank you so much for your advice will definitely try that next year as I can't go through the excitement of watching them grow only to have them disappear again!