In my spotting days in mid 60s I only saw one parachute deployment at LHR which was on A Swissair Caravelle III which landed on 28R and maybe had a brake problem or landed long since it appeared to me to be going a bit faster than usual altho from my head on position hard to judge. Suddenly out pops the emergency braking shute and certainly helped pull the plane up sharply.
icannot imagine they were used routinely because of the disruption caused. LHR was less busy than today but still regularly had a whole procession of inbounds that ahd to be swapped to the other runway.
I also remember attempted to move.
The Caravelle III didnt have reverse rs and i suppose it could sometimes be a problem if it looked to crew like it would over run. In this case it stopped along way from the end and it was a warm sunny day-no slush snow ice etc b