Mercedes Benz C Class surpentine tensioner

Turn the tensioner anti clock,
the point where it pivots is where the fastner is.
It's about 50mm left of the center of the tensioner.

Do you know if there is a bolt holding it in from behind if so would I need to take the air inlet and super charger off to gain access

To be honest no,
Most of the Mercs I get in are diesel.
and I admit access to the tensioner isn't good on them either!
But the tensioners are usually similar,
the wheel you see is on a pivot that connects to a fairly large spring casing,
70mm diameter or so and it fits into a recess with a locating tang.
But I got to ask why the hell are your wanting to remove the thing?
Wouldn't be my choice of fun job.

The plastic wheel has melted and snapped which snapped the drive belt and I can't buy just the wheel I've had to buy the whole unit do you know if I can take the wheel off the new one and put it on the tensioner that's still on the car the wheel is held on with a security hex

Is it similar to this Merc tensioner set up ?

https://www.youtube.com/watch?v=iPkRdudwK8M

No it's not the same as that one the tensioner hasn't got any bolts on the front to hold it in place

As stated I mostly do diesels,
but the "wheel" bearing does come off the tensioner.
It's not a security bolt but a standard Torx.