OOO
It sounds like your describing the same thing that happened to my dad while in France. He had just parked the caravan up and pulled the car off when on a full lock, it went heavy and squelled.
Exactly the the same the fluid was there and seemed normaly however it wasnt been pumped around and where it did it was just staying in the two gaiters on the steering rack.
Not having the tools we put the car in a local garage and had the pump disconnected and a bit of pipe circulating the fluid. However this was just a temp fix while on holiday. Means you dont have any PAS.
When home the steering rack had to be replaced.
PS: Sorry forgot about this bit the car was a Vauxhall Vectra but it sounds like the same problem, also could be a vauxhall thing since it was normal to happen to Fronteras.
Cheers
Let us know what it was please