its a 3 hour job + cambelt kit your better off buying your own cambelt kit and giving a mechanic 100 to fit it outside of work (also look along the lines of replacing your water pump exta 30 quid but worth it while belts off )or else tell garage you pay the labour charge and supply own parts cant see it go over £250
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.