She took part in the event based around the beautiful and historic Thurleigh Airfield with fellow member John Kendall.
The venue has been turned into a motor racing track, and the race featured a flat 5km run followed by a technical 20km bike course and a further 5km run.
Pay, who has been competing in triathlons for three years, came third to qualify for the showpiece for the first time, while Kendall finished eighth in his 55-59 age category.
David Bagge also competed in the British standard distance age group championships as the Autodrome, the top level of competition in the UK.
The race consists of a 10km run, 39km bike ride and 5km run, and Bagge finished eighth in his 50-54 age category with a time of 2:04:15.
He and Neil Couchman enjoyed a strong race at Maidstone’s duathlon, a 9.5km run followed by a 42km bike leg and finishing with a 3.5km run.
Couchman, who is in the 40-44 age group, finished second, with Bagge first in age group and fifth overall.
Chris Nieuwoudt was representing the club at Challenge Salou, a middle distance event near Barcelona, finishing 419th in a time of 5:43.33.
The event began with a 1.9km swim, which was to prove challenging due to large swells which made sighting difficult. Many competitors missed the first buoy and had to swim back to find it.
The 90km bike route was on smooth roads with long inclines and strong coastal winds. The final 21km run leg took in four laps of the beach front which was lined by throngs of locals coming out to support. Nieuwoudt finished in 5:43.33, 419th overall.