They say they were "treated like criminals"...
http://www.bbc.co.uk/news/uk-england-lincolnshire-29100205
"What is an immigration removal centre?
Removal centres are used for detention in cases where people have no legal right to be in the UK but have refused to leave voluntarily
A minority of detainees are foreign national prisoners who have completed prison terms for serious crimes and are being held in detention while steps are taken to remove them from the UK......"
Seems they are criminals so whats their problem ?