Paul T. -
Portush is certainly a contender for the best 36 in GB&I, especially for the best links 36 in GB&I. I was fortunate enough to play both courses there in 1994. The other contenders (that I can think of) would be Saunton, Turnberry, Gullane, Ballybunion and Dornoch (the only other 36 I have played). Don't forget the Old & New at St. Andrews!
I have played the 36 at Sunningdale, Berkshire and Wentworth (East & West). It is hard to imagine a bigger slice of paradise than the 36 at Sunningdale.
DT