the first major change to the SL was in summer 04 .. when COMAND went from CD to DVD based. DVD COMAND has no trim around the unit. CD does.
Most cars from 54 plate onwards will have the DVD COMAND.
In summer/autumn 06 (I think), the SL was mildly facelifted with the 55 getting more power, and the front and rear bumpers changed. The number of bars on the front grill was reduced.
Then in 08 the SL63 came out with the Vauxhaullesque nose treatment
At least the Vauxhall matches at the front and the back, the new SL looks like 'Barry' has spent his paycheque on the front while he waits for next month's cheque to do the back. It just doesn't match...