Here in Colorado where we have hills ten miles long, boiling the brake fluid is a relevant issue. It's rare to take a trip into the mountains without smelling burning brakes somewhere along the way. I guess that you'd be hard pressed to find a long enough hill in the UK to boil your brake fluids. On the other hand, all that rain you get has to go somewhere so it'll end up in your brake fluid and ultimately cause corrosion in the system.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13