Who's panicking? David Cameron didn't impress much EU leaders with his 'Juncker or me' threat, did he.
You can't be part of a team and then continuously stall or block it for personal/national interest. it's give and take.
And please don't think the UK is the only country suffering from excessive migration, we all have our migration problems and it would be very naive to think they will suddenly disappear by abolishing the EU.