thabks for the answers guys.
FO, it is being used in a handheld drill so I don't think a D bit would be of any use. My first thought was using a spade bit, but after showing one to the guys doing the work they decided they didn't want to use one for some reason??? It would be the easiest and quickest option

BT, I had also suggested a pilot hole and then follow with the 14, but it is being used in a production environment and would add too much time and an extra process. Turning the shank down to 10mm myself might be an option. We are going to need a few of these drills as we have a couple of thousand units to do just to start with, hopefully a lot more to follow if we get it right.
cheers again for the replies
daz