OK... So I can chalk off a couple of the issues straight away (replying to myself a little bit!).
First is the heater matrix illumination. They make this fun to get to, don't they? Pulled them out and picked up a couple of replacements for £1 each from the local halfords. They're a 286 bulb for anyone interested. Many thanks to the forum's guide which helped me along with this.
Seeing as this job required the stereo out it kind of kills two birds with one stone to sort the stereo out. The car only has 88k on the clock and I really don't understand how you could be ham fisted enough to scrub the markings off the buttons but either way it'd happened. It's a bit of a personal OCD thing I hate seeing buttons like this as it just feels and looks scruffy and worn.
I had a replacement stereo unit but the code of the stereo wasn't known - so I had to swap the face plates over. The face plate is only held on with two screws but not wishing the guess at whether the LCD on the replacement works or exactly where the code might be stored in the unit, I opened it all up and swapped all the internals into the replacement facia.
Two jobs scratched from the list today then, heater control illumination and the stereo buttons are fixed.
Next up is the replacement headlight, which I'm a little nervous about. Hopefully no rotten bolts on the bumper, should be OK. I have a replacement headlamp unit and chrome trim ring ready to go. Wish me luck.
Have a good day everyone!