Well I've done it at last. I've just paid a deposit for a Skyshed POD, with 3 black lined bays, and pull out shelves.
After much deliberation I decided to go with the POD. I want an observatory that is more robust than a garden shed with a roll off roof, given the winds we get here. The POD also offers excellent wind shielding, and the wide viewing aperture will allow my GPS unit to still communicate to maintain accurate time for the mount. When I approached council about it as well, they decided it would be an exempt development, where a more substantial roll off roof obs would probably not be (though a simple shed would be).
The plan is to pour a pier footing, then a concrete slab around the footing (isolated with expansion jointing). When we move, the POD will go with us and thus leave a bare slab which the new owners may opt to put a shed on. Once I've got the scope sorted and set out to the best height to suit me and the POD I'll order/make the pier to suit.
Construction will start soon!
Al.