Theres no real pattern tbh.
On my 51 plate 1.2 I had no problems, just routine servicing, I had the waterpump changed when the belt was done as a precaution. That had 60k on it.
My brothers 51 1.2 on 53k had a couple of coil packs, an anti roll bar linkage and judging by the irrate answering machine message a starter motor a week after it was sold lol.
My girlfriend Y plate 1.2 16v has 49k on it, thats just had a steering ecu, worked out at £350, nothing apart from that.
My 2000 172 (phase 1) has had a few little niggles, rear exhaust mount, hazard light switch, a cv boot, a drive shaft gaiter and a gearbox selector seal kit. The clip on the passengers window also broke so the window came off the regulator. I ve spent a couple of hundred on it, thats on 63k.
Not too bad really, I have seen some absolute snotters though around the same age though that need a shed load.