@Xantiaman583: Hello, glad to meet you, thanks for the account. Rounded nuts... that's be a nightmare dream I had the night before I dismantled it. You were lucky in the end! Pity about the roll bar getting in the way. I was relieved with the access given on the xantia, once I got to know it (yesterday).
@Citronut and @ CitrJim: All springs, bolts, cups and nuts cleaned up. I'll put it back on today, and try the 'spanner over bolthead, reaching from underneath' method to hold the bolt , just for fun like.
..and to make sure I can do it without a helper , should I break down on a solo run whilst passing through the 'Back of Beyond'.
I have the recessed bolts on the top part of the flange,of course. All I could think of was that they liked the look of it that way..looks stronger, more refined.
It is what finally stopped me getting a spanner on the driverside bolt, when approaching from above.
When I dismantled the exhaust, I was surprised to find no sealing ring: I'll look again. I guess, do not use any exhaust assembly paste at this joint, just the seal?