Lots of pointers there for you Gerry, but I think that on of them, mentioned by Eamonn (silver) above needs highlighting. Were the bushes out of round in their virgin state? You have no way of knowing now of course, but with your new mandrel, you ought to order some replacement bushes too - you're going to need them anyway.
I think it is most likely that they were perfectly round before use, and that the problem lies with your set up. Even overtightening a mandrel, or too much pressure from a saver can cause a problem, but as there are SO many viariables, I think the only thing you can do is to examine each step, one by one.
You've done a kiss test - it's fine.
You've ordered a new mandrel - do a roll test.
Order some new bushes - make sure they're round both outside and in. Make sure the hole is central too.
Examine the relationship between the hole and the diameter of the mandrel shaft - Axi mandrels are notoriously thin.
Mount up your mandrel and run the lathe slowly without the tail stock in place - if you have a straight mandrel from your roll test, you are now examining how true the collet is.
If, in that order, all of the above is working out fine, turn a pen. If the problem still persists, it will most likely be in the centre of the mandrel rather than the ends, and you have nothing left but the fact that you may be over tightening your mandrel.
you can see a overhang at the top of the image.
