The old girl just spewed half the power steering fluid over the engine bay. Only looked under bonnet because the steering started groaning. Normal road driving, not a long drive, about 20 miles.
If your fluid level is low the pump will aerate the fluid as it is sucking it in which is probably the cause of the bubbles you are seeing, top up to correct level and it should bleed the air out (and help you spot leak point)
Well, to finish the story (i wish more peple would share how their tales ended) anyway, booked her into the garage for about a week later. Groaning noises got progresively worse then complete pwer steering failure and no more noise! (can you guess what it is yet).
I had to keep driving (yes, silly I know) for a couple of days till my slot cam up at the garage. By the time I got there pump pully was wobling about and belt half shedded. Needless to say, a new pump was needed!