Hi, I'm just finishing an access to nursing course and am headed for Uni this Sept to study Mental Health Nursing!!
you know how big a deal that is for me I'm sure and well done you on your nursing (must remember to get myself some comfortable shoes for that 5 miles a day). lol
Now.. I was going to suggest maybe taking gym kit with you and running to the bus? Sounds mad but one mile a day initially would be a good run to build up from walking to jogging / running and you could save a bit of time.
There is a great programme on coolrunnings.com that has 'couch potato to 5k' as a schedule name.
Def worth looking at especially if you laughed when I said RUN! lol
I did this programme some years back and did a race for life as my 'goal'
I did get a stitch during a hill part but ran the whole race which was amazing for me.
If that doesn't take your fancy, what about horse riding? If you ring around your local stables and ask about the sizes of horses they have and your weight (don't be shy) you'd be amazed at how many have horses that you'd be fine on and it's GREAT fitness.
I started riding at 17stone and deliberately bought myself a pony who would need me to stay under 14 stone. I got down to 12 and a half but had a baby last year, so gained all of that back. But I'm on the way down again and riding every couple of days. i'm not saying you need your own horse but riding is so much more fun (in my opinion) than a gym class! lol Can you tell I loath the idea of being a gym bunny?
If all that fails maybe swimming? Does your hospital have nearby facilities or perhaps yoru local sports centre gives discounts to NHS staff? I know they do in mine.
Lots you can do, just gotta figure out what you'd enjoy.