Took me a while to find the receipt.
A 2198203226 That's the one i bought. Worked great for me fixed my problem instantly. This is the one with the Beep for locking/unlocking the car.
Bought it for € 86,87 Excl VAT. Bought at a local Mercedes Garage/dealer.
Had my regular garage put it in for me since it had to be there for M.O.T.

Also i found that i had more problems with my broken alarm when it had just rained the other day, don't know if u have the same symptons when wet outside.
Let me know if and how u fixed the problem