No doubt they'll receive a pamphlet explaining why such behavior is naughty, then released back into the general population (Updated)

The Daily Mail obtained photos after counterterrorism police in Britain arrested five men and seized three vans after identifying an attempted terrorist attack on RAF Fairford. A nearby resident tipped police off to suspicious activity. The British Army brought in a special bomb disposal robot with its explosive ordnance disposal team.

Police are holding the suspected terrorists under the Explosives Act after they found incendiary devices and chemicals inside the vans, The Daily Mail explained. 

(Note this for use in the update below) :

The heroic local is understood to have phoned the air base to no avail before she dialled 999 at 12.45am to report men 'acting suspiciously' around the white vans, prompting a major counter-terror operation.

Footage showed the men being arrested and sitting on the road shirtless while handcuffed, indicating officers may also have suspected they were wearing suicide vests… RAF Fairford, in Gloucestershire, is the US Air Force's command outpost for operations from Europe and has been used for American strikes on Iranian missile sites that have been attacking ships in the Strait of Hormuz.

UPDATE:

The Daily Mail

Viable incendiary devices and chemicals were found inside one of the vans, police said. 

The men are in custody on suspicion of preparation of a terrorist act and offences under the Explosives Act.

A bomb disposal robot from the Army's specialist explosive ordnance disposal team was later seen moving between the three parked vans. The rear doors of two of the vehicles were open and what appeared to be large black barrels could be seen scattered outside. 

RAF Fairford, in Gloucestershire, is the US Air Force's command outpost for operations from Europe and has been used for American strikes on Iranian missile sites that have been attacking ships in the Strait of Hormuz.

It was the subject of a warning from Iran's Revolutionary Guard in July, with the regime warning Britain not to allow US bombers to fly from the base.

Today's arrests are not believed to be part of a pre-planned operation, meaning police were previously unaware of the plot.

And then there’s this:

Trump says terror suspects in possible Iran-linked plot to attack UK base were being watched: ‘Looking to do big damage’

“We had them under investigation. They were looking to do big damage to our fort, and working with the British worked out great.”

“We had them under view for a long time and we got them.”

Who ya gonna believe? Sadly, I’m going with the Daily Mail. If these were people already under investigation and “looking to do big damage to our fort”, would the British woman’s repeated calls to the airbase really have been dismissed/ignored?