Advice for summer house build

[johnad]

I intend to start work soon on a large summer house ( home pub )
The plan is to lay a timber floor over an existing concrete base 4 x 2 treated with ply flooring
Then erect the walls using 3x2 studwork and cover it all in 11mm osb
The roof will be 4x2 timber also with osb
Then I intend to cover the walls with some kind of membrane batten it out to create an air gap and clad with 150mm featheredge, the roof will be finished in felt shingles
Inside will be insulated with rockwall slabs and plaster boarded
So hopefully I'm posting in the right place
Do my plans sound ok ?
What membrane should I use over the osb ?
What would be the best way to insulate the roof ?
After doing some quick working out I estimate the materials to be around the £1000 - £1200 mark and if I'm right this will be considerably cheaper than buying a log cabin (my fist thought)
Has anyone had any experience with this type of project or can anyone offer any advice / suggestions before I start
Any ideas that will cut the cost down would be good

 

[angelboy]

Check this guy out, great resource for you:

http://www.ukworkshop.co.uk/forums/build-a-shed-mike-s-way-t39389.html

...and this is one I built last year:

http://www.ukworkshop.co.uk/forums/shed-build-wip-t83913-45.html

Cost Me just over £2k in the end.

 

[big-all]

you don't mention the length width or height