TG in a 152,
I don't have a current flight guide to hand, but looking in my '96 Pooleys there is a mention of maximum altitude in the ATZ of 800 ft when Heathrow Rwy 05 is in use for Landings or Rwy 23 for take-offs. I never noticed that before, but then it is a rare event at Heathrow. Presumably Fairoaks R/T would inform you if that was the case.
05 ceased to exist as a runway a number of years ago, when they built stands on what was the threshold.
23 is only used when the mean southerly crosswind component on the main runways exceeds 25kts. If 23 is in use it's likely that keeders won't be making his trip
It makes for an interesting shift when we are using 23
WF.