Twelve Brits, as well as the women's 4x100m medley relay team, were in action on the third morning in Istanbul and it was Willis who performed best breaking his own English record.
Willis won his 200m breaststroke heat in 2:03.94minutes to rank fourth overall while Jamieson was second his heat in 2:06.05 to just sneak into this evening's final as the eighth and last qualifier.
In the last two major international 200m breaststroke finals it is Jamieson who has come out on top in the battle with Willis first finishing fifth to his eighth at the World Championships in 2011.
Jamieson then famously took silver in the 200m breaststroke at the London 2012 Olympics this summer in a new British record of 2:07.43 while Willis was once again finishing in eighth place.
However, if the heats are anything to go by, that could all change in the world short course final with Jamieson 2.48seconds shy of fastest qualifier Japan's Akihiro Yamaguchi and Willis just 0.37.
Britain's women's 4x100m medley relay quartet of Georgia Davies, Sophie Allen, Jemma Lowe and Fran Halsall are also well placed ahead of the evening session after placing fourth in the heats.
The British quartet clocked a time of 3:54.50 to finish second in their heat behind America and fourth overall with Denmark leading the way after posting 3:53.10 in their head to beat Japan.
Lizzie Simmonds was the only other Brit to qualify individually on the third morning, the 21-year-old sneaking into the evening's 200m backstroke final after ranking eighth in the heats.
Simmonds, who switched from training in Loughborough to Bath following the departure of coach Ben Titley after London 2012, clocked 2:05.65 for the eighth and final place in the medal showdown.
That was 0.18seconds better than Hungary's Evelyn Verraszto in ninth while fellow Brit and senior international newcomer Georgia Hohmann was 20th overall in 2:10.64.
And, while Simmonds just about reached the final, teammate Jazmin Carlin suffered heartache as she narrowly missed out on a place in the 400m freestyle medal showdown, also tonight.
Drawn in the first heat with just two others, Carlin's time of 4:05.13 was just 0.02 shy of China's Zhou Lili who was to take the eighth and final place in the final as the Welsh swimmer ranked ninth.
Carlin was joined in the 400m freestyle heats by Eleanor Faulkner who ranked 16th overall in 4:07.72, 4.23 behind in-form Hungarian and fastest qualifier Katinka Hosszu.
Plymouth-based Ruta Meilutyte could well be on for another gold medal in Istanbul after qualifying out of the 100m breaststroke heats as the fastest with Brit Allen also advancing in 15th.
Meilutyte, who won the 50m breaststroke title on the second night, clocked 1:04.69 to lead the way going into the semi-finals while Allen was 2.24 behind in 15th.
Hannah Miley, victorious in the 400m medley before finishing fourth in the 800m freestyle, joined Meilutyte and Allen in the heats and ranked 29th after touching home in 1:08.68.
Elsewhere Ieuan Lloyd continued his trend of breaking Welsh records with new marks in both the heats of the 400m freestyle and 200m medley although neither were good enough to advance.
Lloyd clocked 3:43.70 for 15th in the 400m freestyle, where only eight progressed to the final, and 1:59.90 for 28th in the 200m medley, where again only the top eight advanced.
Teammates Robbie Renwick, in the 400m freestyle, and Roberto Pavoni, in the 200m medley, could not make it out of the heats either ranking 30th and 21st respectively.