Now all sorted and running like clockwork ....
Gave up on the shoddy header in the end and had the village blacksmith cut the inlet off the factory one piece unit. [his cutter is bigger than mine. lol]. Also had to grind down x2 of the original stud shoulders as the Webcon inlet mounts sat 3.5mm lower.
The car drives beautifully as is ... but will check the overall jetting on the rollers when all's bedded down. Happy days ....