Jamies/Scott the reason why Deal, Sandwich and Princes are far drier than the west coast links is the prevailing wind dumping the rain on western Britain.
And also the easterly winds are drier since they're continental rather than from the open sea.
I play probably 100 rounds a year at Prince's and I believe the winds are much more evenly distributed. I wouldn't say we get anything like 75% from one direction. I agree with you that east in summer is the rarest.