Make sure your engine mounts are in good order or the exhaust will simply get shaken loose.

It is a totaly adequate system, however if the flange has been damaged you will never succeed in getting a good seal.

The flange is damaged by movement of the engine.  This means that engine mounts, stabilizers and subframe mounts must be in good shape.  Then, you need to be smooth both on and off the throttle when driving.

I never put anything between the surfaces.  Good surfaces, hold fast but not too tight with a small jack and then tighten the fasteners evenly.  This should be no big deal.

Thanks, I will give the jack a go.  

Unless Jessie is very strong, he may not have been enough. You need enough pressure that it is just about enough to begin lifting the motor. I think the idea around the joint design was to provide for a (very) wee bit of flex, but more to allow for differential expansion of the cast iron manifold and the mild steel exhaust tube. If it was a slip-over-and-clamp joint like a pipe-to-muffler joint, whichever (the cast iron or the mild steel) expanded the most would leave the joint loose and blowing. Just about all cars of the era had butt-type joints with flanges or bells that allowed for differential expansion. Once you get it right, it generally stays OK.

Thanks for all the suggestions, I fear I need a glob, not a smeer of high temp silicone, however!  Thats the one thing I haven't tried, yet.  I did the " jack thing" although my son is called "Jessie" and he held it in place.  I did the tighten one bolt at a time and then the rest, etc. It seems they were out to lunch when designing this part of the car.  The exhaust lip should have been wider to slip over the manifold and then be attached!.

Put a smeer of high-temp black silicon on the joint

And other brackets have to be slack until you get it snugged up. Tighten the two clam bolts evenly. When it is tight, then connect the bracket that connects to the differential case. Then do up the rest of the system.

make sure the pipe makes a good fit with the manifold! i use a jack from underneath to keep it tight as long as i tighten the bracket..

Any ideas on stopping the exhaust leak between the exhaust  manifold and exhaust pipe?  I have already  installed the new two bolt bracket.  Could it be related to my other post " blue smoke of death"?   You have to be a contortionist to be able to tighten those bracket bolts, hang on, any bolts on a Mini!