Its very common for people to do biomedicine or biochemistry, then finish their degree and realise that they don't want to work in a lab the rest of the lives. But, still wanting to work in something health related they then go and do a 2nd degree in a vocational healthcare subject. There's a few radiographers in my radiotherapy department who went that route.
You would start as a Band 5 radiographer once you qualify, check Agenda for Change website for the latest as its all in a bit of a flux with the strikes at the minute. Compared to working in a lab with biomed, I would say they're roughly similar for a newly qualified graduate, based upon my previous career working in a lab.
Placements aren't paid as a radiographer (unless you can get on an apprenticeship) but by 3rd year you can start working extra shifts on bank to get some cash.
Prospects - its what you make of it. You can stay at Band 5/6 for 30-40 years, or you can push yourself to go further. Radiography you can become a reporting radiographer, go into management, do additional qualifications to become a sonographer (very competitive), become a consultant radiographer (lots of work)....Working in a lab, again its what you make of it. One of my old lab workmates got a sideways move into supply chain, now he works for BAe and is in charge of planning the maintenance for the RAF's entire fleet of Typhoon fighter jets!
Maths - there's a bit of physics in radiography. Biomed will involve lots of chemistry. Both have elements of maths.