Hello Ian,
This belt is not only the fan belt BUT the waterpump belt, that's explaining why the engine overheated !
In order to change it, it is not that complicated. No need to remove bonnet nor radiator.
- Remove the airbox + flowmeter so you can easily reach the alternator (2 bolts in wheelarch, behind the shorck absorber spring)
- Remove fan with 32mm big wrench. Be careful, thread is opposite than usual, so you will have to turn right to unscrew
- Loose powersteering pump bolts and remove the belt going from damper to pump
- Loose alternator bolts (one main at the bottom + the one on the tensionning plate) and then you will be able to change the belt going from alternator pulley to waterpump pulley.
Have a look here, it will be helpful
https://classicbimmerbits.com/e30-how-t ... placement/
Take your time and you will make it
=> The most important / difficult in this process is to never put your weight on the wing to not stress it and generate cracks later