You are definitely not too old. You have 20+ years of working life ahead of you and valuable life experience to give to the role. Mature students make excellent health students because they are often good at prioritising and time management, managing stress - making them calmer under pressure and more resilient (essential in both roles which are high in emotional labour). Nursing attracts a lot of mature students, particularly 40+, probably more so than any other healthcare course. Some universities/courses attract a higher proportion of mature students than others, so ask that question at open days, whichever course you go for.
Nurses & paramedics (all registered HCP) have CPD and lifelong learning as requirements of professional registration - at 40 and going into university-level study you're demonstrating that you're still intellectually curious and committed to your personal development. That will stand you in good stead for a career where you have to stay abreast of the latest evidence relating to your practice.