Drummer Romeo Challenger described Oakes as a “brilliant songwriter” and said he “will be in my heart forever”.
Meanwhile, Russ Field, the band’s former guitarist, said Oakes had an “uncanny natural talent to write catchy melodies and lyrics”.
In his tribute to Oakes, former drummer Malcom Allured said: “We became great friends during our time in Showaddywaddy, and we kept in touch over more recent years.
“Thank you for the great memories Trevor, and for the songs, especially Trocadero.”
Speaking to the BBC, Bartram said Oakes had been “an extraordinarily important component to the band”.
He added: “The chemistry was so right between the band when we took off.
“We hit on this rock and roll thing and the reaction we were getting was quite startling.
“We thought we had hit on a winning formula.”