Grateful thanks to everyone who has been kind enough to reply, particularly brakedwell, megan and barry lloyd. I have a whole lot more to work with now and will be following up many of the leads.
I am reliably informed that the Pioneer accident at Farnborough happened because the pilot had been demonstrating the ability of the aircraft to get airborne across the runway and caught the elevator on a light at the runway edge.
Re. the wire guided missiles: The Twin Pin did use them operationally but there were also trials with the Nord AS30 on the Pioneer, images of which can be seen in the Hikoki publication Flight testing at Boscombe Down, The Cold War Years. The book is still available to buy but only at silly prices!