My advice is to measure the length of the screws, if it's a P38, V8, buy a few 1/4" UNC stainless cap head screws from Ebay to replace them and use an allen key rather than p**s about with fancy sockets etc. It's all part of the manufacturers ploy to get you into their workshop and part with £80+/hr labour charges. After all, it's not as if the screws are holding the car together........or are they ???????????