I've seen some comments in this thread to the effect that almost
everyone has a bank account now and should be able to avoid the non-DD
surcharge. But according to this letter to Guardian Money, people
with Post Office accounts can't pay by DD:

Edward Leslie (Your Shout, March 10) thinks we should stop moaning
about the BT £4.50 penalty for not paying by direct debit, because
he is OK. He is obviously unaware it will hit the poorest,
hardest. The only account that millions of pensioners and people on
benefits have is a Post Office card account which doesn't allow
direct debits.

Therefore, they will be unable to avoid this charge and those with
the lowest incomes will each be contributing to the coffers of BT.

http://money.guardian.co.uk/weekly/s...035747,00.html