Installing a tin garage roof - insulation first?

[Landycat]

I'm about to replace a worn out corrugated plastic roof with corrugated steel roofing,but I'm concerned about the inevitable condensation in cold weather.

I'm thinking that I'm going to need insulation,and that it'll be easier to apply insulation before the tin goes on,but I'm not sure what sort of insulation to use,or whether I need a vapour barrier.

I'm hoping for a fairly cheap solution,this is a basic home built structure of about 30m2.

Any help would be much appreciated.

 

[Landycat]

Would it be useful to cover the roof with foil bubble insulation before the tin sheets are fixed down?