I just finished building a workshop for my project. I had just enough room that I could make the building just large enough to put the wings on sans tips, and do the control rigging/checkout and the fuel connections. I have time, but eventually I'm going to need to find a new home for some things if I actually want to do that
I'm not sure how building codes work over there or what construction methods are popular, but here are a few things I did/wish I did:
First, I would have subbed out a little more of the work. Just prepping for the foundation pour took me three months, and framing took three or four more, because I was doing all of the work myself up to that point, with no helpers. The project would have gone faster and made for much less irritation with the wife had I just subbed most of it out. As it was, had I not paid someone to do the roof, siding, and drywall, I'd still be working on it. I learned a whole lot about construction and building codes, though, and I would still do the wiring myself.
If you're going to be doing any of the design/construction work yourself, familiarize yourself with the intimate details of any and all applicable codes and local requirements. It will save you lots of headaches later. I did this; others I know did not.
I placed outlets every 4' (every other stud), and placed them so they'd clear a standard 4'x8' sheet of plywood laying on its side against the wall. That way I could store material and not block those outlets, and I would have plenty of them. Convert to metric and standard UK material sizes as appropriate.
I went ahead and pre-wired everything I could think of. I have a 30A outlet in one corner and a 50A outlet in another corner for future use for welders and/or machine tools. I have a 30A disconnect in a third corner for an eventual large air compressor, and a fourth 30A disconnect outside for a mini-split air conditioner/heat pump. I haven't yet installed any of those items but I put the wiring in before I closed out the walls so I wouldn't have to tear things open later. For a few bucks, it's not a big loss if I wind up not using them. I also placed a pair of outlets in the ceiling for pull-down extension cord reels. Also, make sure your outlets and lighting are distributed across a couple of circuits. You don't want to lose all your lights at once or have to turn all of them off if you need to work on one fixture. Perhaps my method of every wall getting two independent circuits (every other outlet) was a bit excessive, though. Having more outlets is never bad, in a shop or a house.
Speaking of air conditioning, I insulated the entire shop. I think this building is better insulated than my (cheap builder-grade) house. It's helped so far, and when I do finally put the mini-split on it should be very comfortable inside (and therefore making my wife more willing to come help). Heat might be more of a factor for you; here, air conditioning is more important.
If you can, run an ethernet cable out to a wireless router in your shop; otherwise, get a range extender if your house wireless performs poorly. Being able to pull up VAF, builders logs, Spruce, and other resources while working is important.
If you can, put in at least a utility sink and running water. I couldn't do this because running water would have been too much of a pain.
Lighting is critical. I prefer 6500K or 5000K daylight fluorescents and LEDs. I painted my walls semigloss white; it shows every little flaw in the drywall but I don't care--it's nice and bright inside.
Make sure you have enough turning room and access to at least get your fuselage out when it's done. If you can, have enough room to back your car/truck/trailer up to your workshop so you can unload. I may have cut mine a bit too tight; I can back around to the shop but trying to turn the truck to actually get in will involve an 8+ point turn. I haven't yet actually tried it, and probably won't until I have some gravel down in the "driveway" to it. Unloading the fuselage kit last night, I had to back up to the door and unload it piece by piece from the bed.
If you close your walls up, document where your electrical and such is running before you close them (might be a good idea for your wings, too!) Figure out a way to mark stud locations so you know where they are later.
