My wife’s 200 SLK R171 has been the apple of my eye since we got it. But she put petrol in this morning and it won’t start. The AA have attended and have checked fuses, ”switching” and fuel delivery, but haven’t checked somewhere they can’t get at below the supercharger. When you unlock it then turn the key ready to turn it over there’s a rapid clicking brrrrrrrr noise for a second from the boot but nothing visible at the site in the boot. The sound isn’t normally there. Help please!! Deciding whether to book recovery. Many thanks in advance for any advice.