I've seen plenty of jobs advertised by the big bookmakers and, generally, the pay seems terrible. Even management posts (around here in East Anglia) don't pay a great deal more than the national minimum wage.
As examples of pay levels, see these ads:
1. Deputy betting shop manager. (Starting at �5.77 per hour, rising to �6.50 per hour, in Grimsby):
http://www.jobcentreplus.gov.uk/Internet/viewV acancy.do?selectedVacancy=3&ref=GTT/15993
2. Deputy betting shop manager. (�18000p.a., in Harlesdon, London):
http://www.jobcentreplus.gov.uk/Internet/viewV acancy.do?selectedVacancy=1&ref=WIL/21317
Also take a look at the hours in that second ad. They're 40 hours per week, over any 5 days, between 0830 and 2200. Betting shops are always open on Saturdays, and often open on Sundays. Frequently they open until well into the evening. So employees are working 'unsocial hours' for fairly low pay.
Chris