Staff at the centre spotted the stricken man and called 999 at 8.39am last Thursday.
A rapid-response vehicle and a double-manned amb-ulance were at the scene by 8.42am, having been nearby for an unrelated incident.
The air ambulance arrived at 9.19am and the man was stabilised following what South Central Ambulance Service described as a "medical emergency". He was taken by road ambulance to Frimley Park Hospital, where he was treated.