The big Asda stores sell 240s if you have one close to you. Was in there at the weekend but as I'm stocked up on them I didn't look to see if there were any on offer.
I would never dream of using teabags for myself - I always make a pot of tea with loose tea, even for just myself. I only buy teabags for my husband and daughter who think it's easier if you only want one mug. To me, dangling a teabag in a mug is just gross.