From the Criminal Justice Service website:
Fine
Fines are penalties available to courts for a wide variety of offences. In the Magistrates' Courts offences that attract fines are subject to maximums from level 1 to level 5.
Level 1: £200
Level 2: £500
Level 3: £1,000
Level 4: £2,500
Level 5: £5,000
There's no limit to the amount the Crown Court can fine, but the amount will take into account the seriousness of the offence and the offender's ability to pay.