UKguy, I've run both of those you mentioned and they were both tough. But Parly Hill gets the nod though for sure. The other one that comes to mind is where Reebok holds the Birmingham cross race. That course is a bastard when it's wet too. I've only run it once and it rained for a few days before and then for the whole day of the race. You had to cross that bloody creek 4 or 5 times and the far bank was so muddy that people were falling left, right and centre. All that said, I finished with a smile on my mud covered face as I could only have fun that day. I could not get a decent stride going for the life of me!
Back in Alberta, I'll put a vote in for the Camrose cross country ski area (near the gun club) where they used to hold the odd race. There was no flat on that course and I'm not sure I have ever hurt so much in a cross race. Thanks mostly to Jon Luckharst!