Only ones I can think of that ask for Maths are Bristol and LSE, good degree is subjective depends on what you want to do with it. For roles in Marketing a degree in business is certainly helpful but be aware some companies will prefer Marketing degrees specifically either at undergraduate or postgraduate level. Salaries on average for business degree holders will tend to be in the low 20s (£21-£22k) but from universities such Nottingham, Warwick and Manchester it's 25K+ for unis as Loughborough, Bath and St Andrews you're looking at £27k+ and for LSE and Cass (City university) £30k+. Marketing graduate programmes will vary wildly in salary but at tech and engineering companies such as Virgin Media, Jaguar Land Rover, BT and others it's in the high 20s to low 30s and at banks a little more. If you're looking to enter the worlds of high finance or consulting with your business degree you could be looking at £45k+ for investment banking, £35k+ for Asset Management and £32k+ for Management Consulting but for these ensure that you're at a top university (plenty of information available as to which ones) and try to get some good work experience e.g. internships, in fact work experience is crucial to maximise the value of any non-vocational degree such as business.
Edit: Don't hesitate to ask any other questions but please try to do some research first!