during year 10, i personally didn't do a hospital placement as its very hard to get without already having links like family members and stuff, otherwise u need to be 16 usually. id recommend doing something care related tho like at a primary school which is what i did. shows your ability to communicate well with children, and i also had an intersting experience helping a child who looked pretty ill get the help they needed. this isn't really necessary though and doesn't give you the insight into the hospital environment. obviously ask hospitals, but you might just have to wait till you are 16.
now im in year 11, and back in november i emailed the hospital again, this time asking as a 16 year old, and ever since ive been on the waiting list for summer. its not hard to get spots, you just have to be proactive and be early. (also im not actually 16 till june but they dont know that lol)