The family of three suspects held following raids by anti-terror police say the men have done nothing wrong.
Ansar Khan from Crawley insists his son Ahmad is innocent
Ahmad Khan, 18, Omar Khyam, 22, and a 17-year-old were arrested in Crawley, West Sussex on Tuesday. Five other men were arrested in other raids.
Ansar Khan, father of Ahmad and uncle of Omar, said there was "absolutely no truth" in the allegations against them.
"These boys are the cricketers, the Manchester United fans. Fish and chips is their favourite food," he said.
He was sure the police had "made a mistake" but he had "95%" faith in the British justice system.
Under UK anti-terror laws, suspects can be held without charge for up to two weeks.
Horrified at bombings
Mr Khan criticised the manner in which police raided his house to arrest his son and he was "very angry" when his son had to be dragged from the house crying for his mother.
"They explained nothing. The warrant was shown after 20 minutes, and they wouldn't even let me answer the phone," he said.
Sajjad Ahmed, uncle of another man who was arrested in Crawley, said that his nephew was horrified after the Madrid bombing.
"The majority of those people voted against the war in Iraq, and here they are civilians, slaughtered. Those were his comments not mine. So does that sound like a terrorist to you?"
Tipped for England
Mr Khan said that Ahmad was a "very quiet boy" and a "good Muslim" but had warned him about going to a local mosque, saying: "I said, you read books by scholars. [Those books] are true, what they tell you at the mosque is not."
Mr Khan said Omar had been to the Pakistan-Afghanistan border, but had no involvement with al-Qaeda.
He said the family had flown out and brought him home after about six weeks.
"My cousins are intelligence officers in the Pakistan army, and they helped us find him," he said.
He went on to say that Omar had been a keen cricketer and had been tipped to play for England one day.
Omar, who studied for his A-levels in Reigate, Surrey, once captained Sussex under-18s.
About 700 officers from five forces carried out searches at 24 addresses in south-east England early on Tuesday morning, following weeks of surveillance.
Eight men were arrested, and detectives seized half a ton of fertiliser, of a type used as explosive in the Bali and Istanbul bombings.