Hold on a minute, @HastingsDirect, how do I know I'm not entitled? I mean, you sent me an email saying that if, as I do, pay by instalments, you'll pay not only the higher rate difference but interest, too. I mean, you even list the date I renewed!

So are you saying not only did you 'mistakenly' overcharge, but you've now mistakenly offered a refund? Are you sure you haven't made another mistake, and I should be refunded?