Hi guys.
Just read your post Jamie - after doing pretty much what you said myself
I simply replaced the resistor pack by cutting the power feed (once i managed to get it out of the hole far enough) and used a junction box to connect the new resistor to the existing wire.
Wiring loom that plugs into the back of the resistor was all fine - apparently my car (2007) has the updated loom on it - so didn't need to replace anything other than the resistor.
All is now working fine