Thanks for the comments and advice.
After a fair bit of searching, removal of plywood panels and taking photos underneath, I found myself unable to remove the battery unaided and reluctantly opted for a home start from my breakdown insurer. There was no access from above, no vertical "ally" panel and I just couldn't quite get myself under the car to lower the battery.
But, of course, it started first turn with a jump start using the starter motor terminal. I then slightly nervously drove direct to my Morgan dealer where my P4 now resides awaiting a new battery.
This is my first mechanical/electrical problem after eight years of ownership, so perhaps not too bad; but these insights into Morgan construction and the variability are not what one might call 100% positive!!
All best, Andrew
2005 Plus 4
