Jeff Layman pretended :
Of course, it doesn't matter if you overpay by £10 a month does it? You don't
really don't miss interest on that £10 as the interest rates are so low. Now
multiply that by a million for the total number of customers the company has,
and that £10 million can generate a nice amount of interest for them.

Of course there is at least one company, which pays you interest on any
over payment. More than the interest you would get from the best bank
account.