I think that all overdraft charges are being scrapped and they will just charge interest on the overdrawn balance.
This will work out cheaper for smaller, short term overdrafts, eg a few hundred pounds or less for a few days each month, even though all banks are moving to a scary sounding interest rate of around 40% pa.
£18 a month sounds like a lot for a bank account, do you make use of all the extra services?
But if your'e overdrawn regularly by more than the odd few quid, you need to take action, as the interest could add up significantly.
Look at the advice on MSE. If you change banks, there are a few that give a switching incentive, so the lump of free money could help you pay off your overdraft.
Another technique could be to do as much as your normal spending as possible on a credit card, which is then paid off in full every month but as the money to pay for these spends is in your current account until the bill is due, it effectively reduces the time/amount you are overdrawn, and hence the cost.