Thanks for all the responses to this quandary...I'll try and answer / summarize them in one response.
The wheel manufacturer is https://www.fastwheels.ca
they have a good reputation and I know the shop that I bought the wheels from will help out; the owner is a great AMG enthusiast and besides his GTS and CLS 63 he has on order the GTR
but he is up to his eyeballs right now in his shop with the winter tire change over so his shop is manic. After he rebalanced them a few weeks ago he said if the problem continued to come back in the Spring. Now at the time of the rebalance he mentioned that it might be the alignment or tires as a couple of you suggested. I asked him to go ahead and change the tires but he didn't have any in stock at the time as his shop was full of the winter tires ...not summers. The trouble is that the weather has continued to be great even for this time of year so there is plenty of motoring left yet before going into hibernation.
At the time of buying the wheels I swapped the tires over from the OEM rims as the rears had just been put on a couple of weeks earlier and the fronts had a ton of tread on them; the wear on each tire appeared even across the tread - the fronts were on the car when I bought it roughly 20,000 kms ago and had just been put on a week before I bought the car. All four corners are Continental Contisport Contact 5P. I have had others look at the tires and they seem to agree that they don't need changing; however given the response to my dilemma by some of you this a serious consideration
to fixing this problem despite the amount of tread on the tires. (I hate throwing good stuff away and $700 on two front tires may not fix the problem)
The off set and bore were different than OEM - OEM wheel nuts were not reused a new set of MB nuts in black were ordered as I had the new wheels powder coated black (they only come in Titanium and bronze)
The alignment is near perfect so I don't believe that to be the problem; take your hands off the wheel and it runs perfectly straight down the freeway without any deviation unless the camber of the road takes it depending on which lane I'm in.
Thanks for all you responses....I think I will try putting new tires on the front despite the amount of tread remaining as I intended to change them in the Spring anyway. For those interested
I'll keep you updated.