Wyliecoyote, I hope you contact the UK Crossfire groups listed above. They will have info as to mechanics that can work reliably on your car. Can the water pump make noise, yes, but how do you know it is out of alignment? You can see the belt rotate as the engine idles in park with the hood up. Is that belt wobbling, or not running true. Just look at it. The tensioner pulley goes bad more often than any of the others the belt drives. Did the same person tell you the ABS "ring" needs to be replaced? Cause that is highly unlikely! As I mentioned in my first post each wheel has speed sensors ( they are the electronic pickup at each wheel) and they go bad. They pick up a signal as the reluctor ring which is solid and part of the wheel rotates as your car moves. Those solid reluctor rings do not go bad. Far more likely the speed sensor goes bad. So what ABS "ring" are we talking about?
These are all minor concerns, so get some good trust worthy input. Meet up with someone from a Crossfire group in the UK and/or go to a good Mercedes mechanic.