Forgot to mention to spray all attachments liberally with plus gas or similar i advance of "trying" the hidden bolt. There is a slight depression in the top/side of the subframe which leads to the captive nut, through which you can spray with easing fluid, using the straw attachment. Access is from under the car at the front of the subframe using a six sided socket and short extension (and/or a flexi drive). I used a very long breaker bar but access is limited to a part turn only. Don't attempt to use a 12 point or it may slip and then you are banjaxed! If that fails, it's a subframe off job!
