ATF in my power steering

[snotrag]

While investigating a noise that appears to be coming from the alternator or an idler, I noticed a lot of fluid on the LH bank of the engine, under the PAS overflow. Thus, I've checked the reservoir, absolutely bone dry.

Then I've noted, the fluid pooled on the engine looks suspiciously like Dark Red ATF. Some has come out of the overflow tube, Some has also clearly come from the lower end of the plastic reservoir. There's a lot of fluid pooled about, I'v owned the car for 18 months and shamefully never spotted this. I am presuming previous owner has refilled with the wrong stuff.

Is it likely that the ATF has caused seals in the pump or res to fail and hence the leak?

I have a litre of Pentosin on the way - is there an easy return line I can whip off in order to fully purge the system? Chances of any lasting damage elsewhere?

There no other symptoms.