The plane-spotters deny any wrong-doing
The group has been told their cases will be reviewed by three judges on Tuesday.
Despite claims by the Greek justice minister that national security was breached by the group, MEP Richard Howitt says the Foreign Ministry had been encouraging about their prospects.
One of the 12, Paul Coppin told the MEP he had been questioned about a visit to Turkey earlier this year, as an aviation journalist guest of its armed force.
But fellow plane-spotter Wayne Groves, speaking from Greece, told BBC Radio WM the Greek authorities were "clutching at straws" by suggesting their tour leader was working for the Turkish Government.
'No evidence'
"During May, there was a big air show for the 90th anniversary of the Turkish air force," he said.
"Hundreds of British people went, and Dutch. They are just clutching at straws."
The group of 11 men and one woman deny the spying charges, which carry a 20-year maximum sentence.
Mr Groves added: "It is all based on one allegation by a captain who says he saw us taking pictures at an air show, which is complete lies."
Mr Groves said group had been transferred to Nafplion prison, about 56 miles southwest of Athens, where they were given beds to sleep on.
They had previously been forced to sleep on the floor while in prison in Kalamata.
Free flights
"We are OK. We were removed several days ago to a new part of the prison because we were sleeping on the floor before, but they have now found us beds.
"There are 13 of us here and we all get on well. I feel more sorry for Lesley Coppin in Athens, who is on her own."
The party were given an added boost when the Greek-born founder of EasyJet, Stelios Haji-Ioannou, provided flights for their families to travel to Greece.
He also said he was prepared to be an expert witness for the case given his experience of the British airline industry and British plane enthusiasts.
Mr Groves was waiting to see his father Don, for the second time since he was arrested.
The 12 in custody are Paul Coppin, 57 and Lesley Coppin, 51, of Mildenhall, Suffolk; Peter Norris, 52, of Uxbridge, west London; Antoni Adamiak, 37, of London; Andrew Jenkins, 32, of York; Wayne Groves, 38, of Tamworth; Michael Bussell, 47, of Swanland, near Hull; Michael Keane, 57, of Dartford, Kent; Steven Rush, 38, from Caterham, Surrey; Christopher Wilson, 46, who lives close to Gatwick Airport; Graham Arnold, 38, from Ottershaw, Surrey; and Gary Fagan, 28, from Kegworth, Leicestershire.