UKVI have published the quarterly illegal working figures for 1 Oct to 31 Dec 2017:
Across the UK: 624 penalties; 990 illegal workers; penalties of £1,815,000 levied

Interestingly they have published who has been fined in all regions except London and the North West. Makes me wonder if there is some challenge. The single biggest fine was in Scotland to a value of £75000.