Well, I have 8 sheets of westfoam board at the moment. It only cost £20, so I'd like to try using it first before ordering more. I know everyone says it's heavy, and no use, but I'm going to experiment with it. I want to use it to practice building a model, even if it ends up not flying, I'll learn how to build with FB.
I was trying some things with it this morning, and found that I can easily remove the paper by running an iron over it for a few seconds, so that removes some weight. Also, it can be folded over if I leave the paper on one side, then score the other side.
And anyway, buying this FB isn't a total loss as I can build other things with my son and put a raspberry pi in it. We also built a water bottle rocket last night, and made fins with it.
I've no idea but unless you have a specific reason for NOT using FT foamboard, then just buy it from whatever store is closest, Sussex Model Center, Leeds Models etc. all sell the stuff, that way you know you are using the correct foamboard for the job and not cutting corners or making your model 40% heavier for the sake of saving 75p.
A Bloody Barron costs between £4 and £6 a throw depending where you buy the FT Foamboard from, the guys at the field scoffed at it until they realised how cheap they were to build and how quick they can be put together (2 hours).
I don't live near any shops that stock the FT board, so I'd have to add the cost of delivery.