I can't break it down, but I can tell you the overall difference between the Fairey single and two seat NAD 925/39 designs:
Griffon powered aircraft with 4x cannon
Single seat: 9,380lb
Two seat: 9,850lb
Difference: 470lb
Sabre powered aircraft with 4x cannon
Single seat: 10,880lb
Two seat: 11,350lb
Difference: 470lb
All a bit neat with both coming out the same, but NAD 925/39 was put together very quickly. Interestingly the Firefly FR.1 is quoted as 14,020 pounds so the original estimates were very optimistic.