I think you mean the “drive shaft”. I believe your A 150 is front wheel drive, meaning it has two drive shafts, one on the left, and one on the right. I’m presuming then your left side drive shaft is the problem. You must be in the UK, b/c the left side there is the off-side. Plus your price quote is in pounds. In the USA the left side is the driver’s side. fyi, in the USA the terminology would be “axle shaft” rather than “drive shaft” for that part.
The Mercedes A150 isn’t sold in the USA as far as I can tell. It appears to be a smaller entry level Mercedes. hmmm … ok, I can tell you the price to replace the left side axle shaft for a 2006 Corolla: about $500 for the part and 3 hours labor, figure appx $800 total. That’s roughly 600 pounds. So if you can it done for 200 pounds, that seems a very good deal from where I’m sitting. I’m thinking however that the problem part isn’t the axle shaft, b/c of the cost discrepancy. Ask you shop to clarify which part they are replacing. Maybe it is just one CV joint.
One pretty common problem we hear here about axle shaft replacements is the wrong part gets installed. That’s causes all sorts of problems you don’t want. On the Corolla there’s probably 8 different part numbers to choose from depending on where the car is built, if it has abs or not, manual transmission or automatic, XRS or not XRS (whatever that means). So make sure your shop is a experienced w/Mercedes repair, and ask them to double check the part number they are using is compatible with your vehicle. Best of luck.