I used to be an electrician. I don't know anything at all about Finland's electrical code, and I imagine that you use a metric wiring sizing scheme over there that I know nothing about. But if there is anything you are unsure about, I will try to help you out. I am pretty dumb though, but I will try.

I have a similar thing going on at my house: Very limited electricity while my floors are torn out for replacement. The original wiring was left over from the 1950s and was ungrounded asbestos-wrapped cloth cable stapled on the outside of the walls. Very unsafe, so I ripped it all out.

I installed a service disconnect on the outside of the house, to make it easier to comply with the electrical inspector (so he wouldn't have to go inside and see the mess of ancient wiring that I was tearing out, even though it was no longer hooked up). That will make it easier to run power to my motorcycle shop and barn once I get my buildings moved/built there.

I put a GFCI receptacle on the outside of the house, wired into a breaker in the disconnect, and ran an extension cord through a window. At the moment I have the old panel box inside hooked up on the feed-through lugs, too, and a couple of receptacles on it in that one little room, and still extension cords everywhere. I am going to have to tear out the old panel box and put in a smaller subpanel, though, and then I will reuse the feed-through lugs and the big panel in the barn for the arc welder and stuff.

So at the moment I am just using the electricity to run a chest freezer converted into a high efficiency refrigerator and my power tools. I am lighting my house with oil lamps and cooking on an hand-pump Indonesian kerosene pressure stove.

I actually like it that way, though. I am going to continue to use kerosene for lighting, and I am waiting for a modest mutual fund to mature, and then I am going to buy one of the high efficiency Amish wood-burning cook stoves. They are way better (and safer) than the old Monarchs and stuff that people were cooking on around here in the 50s and 60s.

That house already burned once, back in the 1940s (fortunately it only burned the part of roof off before the rain put it out, and they were able to fix it instead of tearing down the house)... I don't want to burn it again! Lol.

Like many things that seem "old fashioned", I think that eschewing a certain amount of convenience helps me to be more thankful for what little I have, and to be more grounded and humble. Indeed, I really like the ideal of the simple lifestyle that the Amish and the Old Order Mennonites have going on, except that I am not really on board with the particulars of a good many of their religious beliefs... :3

Anyway, I look forward to seeing your progress on your house-work, too! I hope that maybe we can share ideas and stuff as we both continue on with our projects. :D