Should they return? no of course not, but I would go further ANY place that allows the conversion to Jihadist movements should be closed (a holy war by very definition is against all equality laws in the UK) – be them places of worship, cafe’s whatever.
If the Islamic community (who are 90% moderate and rational) won’t allow this to happen, it won’t. A mainly Christian, capitalist, western society like the UK stands no chance of changing the minds of ideological fundamentalists so we need to make sure we get them out of the UK, keep them out and help the Muslim world get rid of this heresy to their belief !!!! (someone get me on Paxman !!)