As I'm in the final design stages (i.e. we've decided it's a good idea) of a rather big shed, I immediately empathised with this one. The first thing to do is have a look at this ...
http://www.ecobase.biz/
... which was a complete eye opener for me. This isn't the only thing on the market - there are quite a few similar systems.
Second thing ... planning permission (at least in the UK) doesn't depend upon the building material, but more on overall size, height certainly, distance from boundaries and the building line, and whether you had corned beef for tea last night. Most garden sheds/workshops don't need it (mine will have a maximum height of 2.5 meters as it will stand almost directly upon the boundary - but that seems plenty to me).
Breeze blocks - there are a million versions with/without holes, cement/cinder construction, etc. But, to be quite frank, there's no reason why a well-constructed timber frame with good, solid panels shouldn't withstand even an Irish full frontal wind assault. A wooden shed is HEAVY without the aid of modern construction materials. And, let's face it, you're going to be hard put to find a 16th-century survival of the breeze-block technique. I'm going to be using WBP ply on a tannalised frame (translation: - exterior-use plywood panels fastened to a 4x2 mesh of treated timber) - which is about as structurally rigid as you can get.
Roofing - ah, there lies the rub! If you face a single-slope lean-to type of roof into a gale (higher end forwards), you have a pretty efficient lift-off machine. You could, of course, turn the whole thing round to deflect the wind rather than oppose it. Or go for a straightforward gable design (as on your house). The second is more technically difficult to a) build and b) maintain, but it looks prettier. Up to you. In either case, that overhang isn't mere decoration - the larger the overhang, the better the weatherproofing. Again, it's a balancing act.
The single most expensive-cum-important part of your shed-building is the base. If it ain't level, you'll have problems - so that's down purely to time and patience and a spade. Once you have the level surface, the Ecobase kind of thing is far and away the most cost-effective way of proceeding - loads cheaper than a concrete raft and certainly a bank-loan cheaper than foundations.
The most constructive comment I've seen on the net was a good reality check for me. There was someone getting really worried about the shed and regulations and stability and who asked for plans. Some guy came on and pointed out that plans weren't really necessary because it was, after all, just a shed. Having almost got to the same point as the original poster, I managed to rein in my panic after that point. It is, he was right, just a shed, and if it has enough nails and screws and stands on level ground, it would still be standing if it was built next to the Antarctic penguins.
Hope that helps?
Mike
things), Check out this website for some ideas 