FJJP. I sat in the 707 in the hangar at Finningly (I think) several times. There was also a two seat delta (of the same series?) in the same hangar. I was impressed by how basic the instrumentation was and how small both aircraft felt. If I remember correctly, the 707 was painted blue and the two seater was in a lighter colour.
Saying you would spend the sortie with your head cranked over if you wore the hard part of the Mk. 1 helmet was a bit of an exaggeration. There was not that much clearance though. I suppose it depended on how you adjusted the Martin Baker. At one point my "fast-jet" bone-dome was withdrawn and I was reissued with a Mk.1. The helmet that was withdrawn was the type with the visor that stowed inside the hard, fixed protective cover and it had the lowering bar as opposed to the central track with an adjusting knob. Was that a 2 or a 3?