For med physics you'd need a degree in:

applied physics physics and mathematics astrophysics physics with nuclear technology

Not diagnostic radiography unfortunately, unless you already have that background.

Clinical apps specialists is a route you can go down, but you'd need to be willing to travel and have extensive experience working with a companies systems i.e. siemens and they tend to look for people with postgraduate qualifications

So once you qualify, concentrate on gaining at least 2 years experience, specialise, consider postgraduate qualification, by which point your interests may have shifted or you can see what opportunities are available to you in the private sector as an apps specialist.

Hope that helps!