If you've received the standard paperwork which offers you the opportunity to pay the fixed penalty (rather than going through the court process) then, as other have said, it's equivalent to a basic speeding offence. That means a �60 fine and 3 points on your licence.
However, if there's some reason why the matter is not being dealt with through the fixed penalty process, it would be up to the court to decide the appropriate way of dealing with the offence. Without knowing the details (but basing my answer upon court reports in local newspapers), I'd guess at 3 points plus an �80 fine plus �50 expenses.
Chris