I think it is more likely a Britannia tailplane; there is no `external horn balance`,the elevators and ailerons are servo-tabbed,and there is an outer portion of the LE of the tailplane that `appears` to be somewhat discoloured,probably by the engine exhaust/dust.It also appears to have a more symmetrical aerofoil than the 1-11,and is low-set on the fuselage..
You could go to Duxford or Kemble to check.....