Just done mine using Discount MG Rover Spares
ceramic replacement kit
A few tips.
Use the photos on the first page of the thread, they show exactly where everything is and make it a lot easier.
My resistor pack was held in with square headed screws. They tap into plastic so you need a tool to screw them all out. It's best if have a small socket set (invaluable for car work, sting the family for a set for Christmas if you don't have one).
When undoing the resistor pack screws, do the one closest to the side of the car first. It's the hardest to get at and if you undo the other one first, the resistor pack moves around and makes the job harder than it needs to be.
When unsoldering the old resistors and soldering the new ones in place, you'll need to hold the pack in place. I clamped mine in a wood worker's vice - this has wooden teeth and so I was able to do it up tight enough to stay put (you'll be pulling and pushing a fair bit) without damaging it.
Soldering in the three resistor sets is fiddly. There are four contacts. Two of these will have a single resistor soldered to it, the others will have two. Do a single wire first. This then holds that resistor set in place while you solder the other end of it plus the first wire of the other resistor set that goes on that contact.
Of course, if you share my hamfistedness and have a rubbish old soldering iron like I do, it'll be a drama so you have my permission to swear like I did.
Then put it all back together again.
Take your time and it's an easy and satisfying fix. My fan even worked properly after I'd finished.
Thanks for the kit Mat.