Check out the Gladiator on the IPMS Stockholm website.
Eduard have the Sutton Harness wrong. Just reverse the Y and attach it to the shoulder straps. The Y goes between the seat and the pilots back. it then goes through the hole that should be in the lower part of the seat back and attached to a fuselage cross-member behind the seat.
The same applies for the spitfire, hurricane or any aeroplane using the Sutton Harness.
Hope your as slow at building as me. :)