The reason UK went for CBTE, not M/TER, was the same reason as installing the Spey rather than the original J79: UK content, in addition to the slight change in geometry of the shoulder stations. That from the Phantom Weaps School Chiefy of the time, one Dougie H*****stall.
CBTE - Carrier B*mb, Triple Ejector
if GR1 had had two MER fitted on the belly pylons, and each filled with 6 BL755, would performance have taken a real hit?
The Load Teams would have had to put the aircraft - Tornado GR1 - on jacks if the lower station of the CBTE had been loaded, indeed I doubt there would have been enough clearance underneath as the CBTE's were fitted fully loaded and the Handling and Loading Cradle ironwork added quite a few inches under the lower store.