I wouldn't be surprised if there's a false imprisonment claim in there too, as well as whatever ppl succeed in claiming for the delay and inconvenience. Love to see Indian bureaucracy defend itself in a UK court!!
Re the clareview comment about passenger records being sent from India to Heathrow - there will no doubt be questions asked about why the UK citizens on board couldn't simply flash their passports at LGW and then get the train into London - at least one said to the BBC that they were happy to do this!