So, I had my wheels refurbished, to get rid of some kerbing marks... and ever since I did this I have a wobble....
Sorry to hear you're having problems.
Usually, if you get that kind of vibration happening in waves, it means that at least two wheel/tire assemblies are out of balance. The 'wave' indicates when they're going in and out of phase with each other as they roll.
I always prefer the manufacturer's wheels, personally, particularly for high-end brands like Mercedes-Benz.
I had a similar situation when I fitted a set of refurbished AMG wheels to my car. At surface street and local expressway speeds (up to 60mph) they felt fine, but at speeds on the highway (65 to 80 mph) a serious vibration appeared and disappeared in waves.
I immediately thought it might be one or two of the wheels out of true, but an out of true wheel ultimately won't balance on a 'rolling road' type of dynamic tire balancer. I brought it back into the tire shop for a thorough recheck.
They found that two of the wheel assemblies were 25g or more out of balance ... way more than an acceptable amount. They also unmounted and remounted one of the tires as it seemed either the tire was either mounted incorrectly or malformed, it had a small bump in it when spun. It seems to have been the former because after they did that and rebalanced all wheels and tires, the vibration disappeared.
It was sloppy work on the part of a former employee, who had already been let go. "Too many returns when he was running the tire balancing machine. He wouldn't pay attention..."
I hope your problem is solved to your satisfaction soon.
BTW, for those in the USA: I bought my 17" AMG rims from Auto Rim Shop (home
). They're the correct sizing and offsets from the SLK280/350 Sport kit for 2006 to 2009. The refurbishment was done beautifully, they look brand new and run perfectly true.