Twice now I have been reversing with full left lock on to park and heard a clunk followed by the steering dying to the point where the wheel won't move either direction. A few seconds later it comes back on and I can finish parking. Today the same thing happened again but instead of a clunk I could hear what I can only describe as almost a hissing noise.

Is this likely to be the power steering pump on its way out? If so any ideas what it is likely going to cost for it to be repaired? :( Car still works by the way, this only seems to happen for a few seconds when I have full left lock on and then it works fine again.

yeah seems like the power steering, its probably going to be expensive from ford. best option is to get one from a scrapyard and fit it in your car.