An update to the OP
First off, thanks for all the replies so far, including the ones doubting my sanity.
To elaborate a little on my interests - I do actually *enjoy* working with computers, especially dealing with the hardware side of things. I get a strange sense of satisfaction in watching a system I've put together or upgraded boot up and run as sweet as a nut. I also enjoy exploring things about computers that I don't know too well. Manually configuring networks, the dustier corners of Control Panel, mucking around with Linux. Learning new things and then being able to apply them in a troubleshooting context - I like stuff like that.
Of course, I do understand that a large amount of stress comes from computer problems that are not software or hardware related...but then again, I can't imagine it's too different to working with patients. Failing that, there's always the five-pound lump hammer in my IT toolbox as well.
I have done a Computer Studies A-Level in my dim and distant past but the majority of it was taken up with building a database and front end in Microsoft Access, which bored me to tears. We were also taught Pascal which was much more engaging - during the same period I also taught myself Visual Basic. The latter was not such a good idea; I wasted most of my lessons writing an almost passable game of "21" with a basic level AI opponent and forgot to work on the database.
Amusing anecdotes aside, ultimately I'd like to go into network administration, through means of support and helpdesk work (hands on if possible), looking after individual computers and building up from there. Linux support also looks very appealling but I was advised that I'd need some basic level Linux experience first before I'd be able to do the Comp TIA Linux+ course. I'm guessing books would be a good starting point, unless anyone knows of any good online resources?
Once again, I really appreciate the lengths everyone is going to to help me out here. You guys and gals rock.