Been trying to put a new rear caliper on my clio, but cant undo the bolt that connects the brakepipe. I left some wd40 on it for an hour or so to loosen it off but still to tight. then, when i thought it was turning, I noticed that the spanner had stripped the bolt head. What is the best way to undo a bolt that is in this state? Ive tried some grips on it but still no joy. I cant get a socket onto it as the brake pipe runs into the middle of the bolt. Is there any special tool you can buy, or some method?