Kyle Edmund followed up his boys' singles victory by winning in the junior doubles, while British pair Josh Sapwell and Julian Cash also won.
Jonny O'Mara, who Edmund beat in the singles, also lost in the doubles to complete a miserable day.
Evan Hoyt went out, as did Jamie Malik and Robbie Ridout, Samm Butler and Billy Harris and Luke Bambridge and Cameron Norrie.
And three pairs also went out of the girls' competition at the first stage.
Edmund and Portuguese partner Frederico Ferreira Silva are the top seeds.
The Briton returned to Court Four, where earlier he saw off friend and British compatriot Jonny O'Mara in straight sets in the boys' singles.
He had a harder match this time before he and Ferreira Silva beat unseeded Swedish pair Daniel Windahl and Elias Ymer 7-5 4-6 6-3.
Edmund told BBC Look North: "They were very good players. We knew we had to be on our game. We started off well, it was just a shame that we got broke. I missed a few easy volleys so it was my fault we got broken but it was good to get through.
"It was the first time we had played on grass together so we were just trying to figure each other out but we knew if we kept going we would have a good chance of winning."
Britain's Cash and Sapwell beat American pair Stefan Kozlov and Spencer Papa 6-7 (4-7) 6-4 6-4.
O'Mara, playing with Croatia's Borna Coric, lost 6-7 (4-7) 6-4 6-2 to Italian pair Filippo Baldi and Matteo Donati.
Llanelli's Hoyt and South African Montgomery were beaten 6-3 7-6 (7-4) by Australian pair Jay Andrijic and Bradley Mousle, and Malik from Surrey and Berkshire's Ridout lost 7-6 (9-7) 6-2 to Laslo Djere of Serbia and USA's Martin Redlicki.
Butler, who was born in London, lives in Hampshire and trains in Bath, and the Isle of Man's Harris went out 6-4 6-4 to German/Austrian pair Maximilian Marterer and Lucas Miedler.
Nottingham's Bambridge and London's Norrie went down to a 6-1 7-5 defeat at the hands of France's Maxime Janvier and Poland's Kamil Majchrzak.
Leicester's Katie Boulter and Scotland's Isabelle Wallace suffered a 6-0 6-0 whitewash at the hands of top seeds Barbora Krejcikova and Katerina Siniakova of the Czech Republic.
Freya Christie, from Hucknall, and Southampton's Gabriella Taylor went out 6-1 7-5 to the Swiss/Slovakian second seeds Belinda Bencic and Petra Uberalova.
It was Christie's second defeat in two days to Bencic, who also beat her in the girls' singles.
Taylor told BBC South Today: "We had a lot of chances in the second set especially at 5-5. We could have gone 6-5 up and most annoyingly we had two set points but unfortunately that's the game of tennis - you can't always win.
"I have really enjoyed being here but there are many things that I need to take on board with me and next year I'll hopefully come back."
Scottish pair Anne Brogan and Maia Lumsden lost 6-4 6-7 (3-7) 6-0 to Brazilian/Australian duo Carolina Alves and Sara Tomic.