For those interested I went to my local Mazda dealer today, the parts required:-
2 under shields costing £265
I was a little shocked considering they are nothing more than cardboard, I asked were they important and the reply was "your better off without them, they are only there to protect the car if you ground it"
Apparently they are very prone to failing due to being held on by only a few screws, but not covered by warranty if forced off by water. Strange when they are underneath the car were there is water.
So for now I will see if I can get a set from a breakers yard