What exactly do I need to convert to the 172 front brake set up?

[Wobba]

I imagine I would need the 172 stub axle? Do they fit straight onto the suspension?

[northy]

No they need a bit of machining to fit the narrower mk1 struts. Nothing major though

[Wobba]

Ahh yea I think I remember now. Cheers.

[ThRaXaIR]

So the full list is? :D

[16v_paddy]

So the full list is? :D

172 stub axle, machined by 2mm iirc on each side where it attaches to the strut with a mk1 hub pressed into it
calipers
discs
pads

[tutuur]

Bolt holes are different too, so either press bushes into the stub axles or drill the coilover to take thicker bolts.

[kmetek]

You can also use Megane I 1.6 16V stub axels, easier and cheaper to find. The only difference with the 172 is the bearing size, the rest is the same.