Well, eventually got around to jacking up the plus4. So jacked up the passenger side and removed the filler plug, recall I'd already topped up the 'box to a level with the box horizontal. I gently lowered the jacks until oil just started to appear at the fill hole and rechecked the box was level with spirit level, I stopped the lowering.
Taking a measurement from the outer edge of the main forward to aft chassis member with car jacked up indicted that the height to the garage floor was 345mm. As mentioned my car is on 15" wheels and 65 profile tyres.
As a final note, the car's done some 24k with the oil level at "10 degree tilt level" and I can't detect any adverse performance issues in terms of smoothness of gear change or any mechanical vibration or noise due to operating at thjs level.
Many thanks Lowflyer for following up on my request. Following all the debate on this though, I am now inclined to concur with Spanner Juggler’s remarks above, and would not be surprised if most Morgan workshop technicians agreed.
