Pillage and Bryson both came fifth overall and finished as top junior athletes in the senior competition, while Denton finished third and Mitchell fourth in the under-19 event.
In a highly-competitive women’s category, Bryson finished behind 2012 Olympic silver medallist Samantha Murray and fellow internationals Jess Varley, Joanna Muir and Francesca Summers.
The Plymouth athlete recorded 13 victories in the fencing, clocked 2:26.78 for the swim before improving her position with a good laser-run time of 13.45.93 and then finishing fifth and top junior with a good ride time of 1:22.00.
In the men’s event, 19-year-old Pillage was only beaten seniors James Cooke, Sam Curry, Joe Choong and Tom Toolis.
Pillage recorded 23 victories in the fencing before clocking the fastest time in the pool with a 2:02.01 swim to move up to third.
He dropped two positions in the laser-run with a time of 12.51.32, but maintained his spot with a solid ride of 1:29.00.
Pillage finished with a total of 1,359, with Olympian Cooke winning with 1,409. Cooke was the only athlete to top 1,380 points.
In the under-19 girls’ tetrathlon the following day, Denton showed her potential by making the podium, despite being one of the youngest athletes in the field.
Fellow Plymouth College pupil Mitchell also caught the eye having also competed in the senior ride the day before, where she ranked joint third with a time of 1:22.00.
Mitchell impressed in the fencing, finishing second overall. She then moved into the lead after the swim. She clocked 2:23.38, which was fourth fastest, with Denton third quickest with 2:22.61 to move up the rankings.
With no riding event in the under-19 competition, the final order dramatically changed with the combined run-shoot.
Wiltshire’s Sarah Wilson went from 11th to first, with Emma Whitaker moving from eighth to second and Denton climbing four positions to take bronze, with Mitchell just narrowly missing out on the podium with fourth. Just 29 points separated first from fourth.