Thank you everyone for your advice and yes Ian I have been accused of over thinking things in the past!
I am not good with numbers and I am what I call ‘numerically dyslexic’ – measure it twice and cut it wrong once. I wanted to draw a plan up partly to overcome the number business and also be able to work the materials out more easily and have the flexibility to make changes.
Thank you all again, I will keep you posted on progress. Nick.