I have found English Muffins in both Carrefour in France (Ile de Napolean just off motorway to Mulhouse - nearest to Basel) and also in the supermarket at Familiacenter in German Rheinfelden and MarktKauf just across the border into Germany at Weil-am-Rhein where I know many expat Baseler's go but must admit I hate that store!
Never in Switzerland though.
Interestingly the French ones are better - both are labeled as English muffins though

In Carrefour you can also get a wholemeal option.. though I stick to traditional white for these.
Susanna