I just bought a brand-new gas BBQ (at Aldi - very good deal). Where do I now find the gas tank itself and get it filled up? How does this work here in Switzerland?
Pretty much every gas station sells bbq gas. The tank bottle comes with a hefty deposit, around 50CHF, so make sure you keep the paper work they give you to return it.
Most places that offer gas bottle exchange have the new, lightweight bottles (comprising a lot of fibreglass or some such material). Some also have the old, heavy, steel bottles. The difference in weight is enormous. You can swap between bottle types, so try wherever possible to take the lightwight bottles. Your back will thank you.
By the way, gas bottle exchange is pretty much your only option. It's almost impossible to find a place that refills bottles, and even then it's usually only for commercial/industrial use.
Final tip from me: despite the astronomical price of propane in Switzerland, don't even think about buying gas across the border. Their bottles have different fittings which are not compatible with Swiss standards (such as the fittings on your barbecue).
Thank you all, I'm not an expert in gas containers. I drove up to Migros and got one. they had 3 sizes (small, medium, large). I got the small one (12l) and it cost ~50 CHF for the deposit of the container.