A certain degree of nervousness in the early stages is normal; but the lack of confidence that you describe is quite unusual. I wonder what on earth happened at Bournemouth?
I am no psychiatrist, but your subconsciousness seems to be telling you that "Flying is Difficult! Flying is Dangerous! You are not good enough, and you cannot handle it!". As you realize, you must overcome this if you are to have any hope of a professional aviation career.
I don't know of any 'magic bullet', but if you can find an experienced and understanding instructor at Stapleford it would be prudent to confess your specific fears and seek more dual instruction. If that doesn't do the trick, perhaps you will need to accept that you are simply uncomfortable flying, and try another pastime.