DBChopper: We use a lightweight dog cage for sliding into the cargo bay of the EC135. It's tailor made to fit with minimum fuss and the dog gets into and outof the cage while it is in the a/c.
Our CAA flt Ops inspector confirmed that for commercial flights, a dog simply lying on the floor amongst the passengers etc is to be treated as loose cargo which is inacceptable.
PM me if you need details of the kit.