Cheers Clive and Bert, Clive that was exactly what i was looking for :)
One more thing...... Can you check my calculations to make sure I'm right

2 rails 135cm x 4cm wide + 2 bridges @ 77.5cm x 4cm with depth of 6mm
(135+135+77.5+77.5)X4X0.6 = 1020cm3 = 1.02 Litres

1.02 Litres / 4 = 0.255 Litres 209 Hardener
@3:1 ratio by volume = 0.765 Litres of Resin.

Seems the weights are not quite 1 litre to 1 Kg as the manual states the ratio is 3.5:1 by weight.

Regards,

Charlie