Hi, when i recently switched to 3, I had the same question but when I clicked the link on Three+, it asked me for my location (Darlington in my case.) and it listed the cafes nearby like Caffe Nero, Cooplands etc.
Make sure your Three+ app is up to date and, once you claim the £1 coffee offer a website will be linked over to you and there's an option to search for all participating venues.
Maxine
Mod tip! The author of a post can hit 'Accept as Solution', to highlight a reply that helped solved their query.
