Compensation for False Imprisonment guidelines start at #500 for the first hour and slides till it reaches #3000 for 24 hours (The Commissioner of Police for the Metropolis v Thompson and Hsu)
So call it a round thousand pounds for 4 hours unlawful detention, multiply by the reported 190 on the plane and the cops could be in the hole for close on 200k.
Or rather the poor suffering council tax payers would end up paying out, people who (contrary to what bjcc obviously thinks) are entitled to expect the cops are there to make their lives inconvenience free, and also there to protect their 'freedoms' which date back to a long time before Dixon of Dock Green was around.