Quite Draconian new speeding fines have recently been introduced.
The above chart shows the different bands. For example, if you were doing 43 mph in a 40 mph zone, you'd be in band A. The police normally allow a 10% error, so they'd probably ignore 43 mph, but not necessarily so. However, if you were doing 52 mph in a 40 mph zone, you would be in band B.
The following is what could happen:
your weekly earnings.
to 28 days and a fine of up to 100% of your weekly earnings.
days and a fine of up to 150% of your weekly earnings.