If you can't afford the £500+, I think you do need to put your Electronics degree to use

I'm surprised one with an Electronics degree would rely on a drive without a backup. All stuff fails, especially mechanical devices. Also, having a degree isn't going to give you nearly as much help as you may think. From your statements, I suspect you aren't even aware of what problems could occur, or which are most likely. Recovering the data with a no-rom-swap PCB exchange would just be wonderful. However, you can't change the laws of physics, or warp the space-time continuum and make the PCB be the actual problem just because that is within your abilities. If you really want to do it yourself, you can spend the cash on the tools, spend a lot of time learning (That means 90% READING, 8% experimenting, and 2% asking questions), and in only a few years you'll be able to answer most of your questions, and possibly even recover it yourself. You can even save some money on tools by reverse-engineering the drive. ATA commands are documented, and the rest can be figured out by a clever hacker.
Next time you need a Doctor, why not try asking him/her for advice on how you can fix the problem yourself?
I have a bit of a feeling as to what you may say next. I know you won't spend the money to have it done right. The data isn't THAT important. You can do two things. You can mess with it yourself, and not recover a single file, or you can read. Read a lot. That way, you at least will have a chance, or understand how far you're in over your head.
For diagnostics, MHDD is a good start.