Found the hole - hose to the EGR valve had a split in it big enough to put my finger in! Ordered a new set of silicone hoses and wrapped the current one up with duct tape until they arrive. I had parked this up and switched to the Astra until I got this one sorted, but a bloody brakepad delaminated and fell of on the way home from work yesterday! So ordered a new set of pads for that as well.