Hiya GDBN, its always good to meet a fellow Naylor he he !!!!
Ive just had another look under the car and discovered it isnt the centre box at all, its the collars that join the 2 sections together thats touching the bottom of the car.
I got some rubber strip today from work that can withstand temps upto 177' C and down to -46' and put it between the collars and the base of the car ! It also stops vibration
It looks ok but not tested it properly yet as cant get the car to start at all now due to starter motor/ solenoid being no good !
Lee.