Anyone practical with half a brain can make a decent job of a domestic rewire if you have a methodical and sensible approach. It's only single phase and you're dealing with 240 volts on the live not potentially 415 volts between phases or weird stuff like having things with electric motors in them running in the wrong direction (you have to swap two of the phases over in the supplying isolator switch/fuse when this happens).
Most of it is donkey work, lifting floorboards, shoving or pulling cable between point A and point B, chopping out brickwork to sink flush back boxes or chasing plaster for burying cables. The actual connecting stuff up bit is only a small percentage of the total time involved. Much the same can be said of plumbing. it's 10% knowing enough to design your layout effectively, and 90% actually getting access to the places where you need to run pipes. A lot of trades like to blind punters with science, and make out that ordinary Joe Public can't possibly do all this really technical stuff themselves, but it's mostly hogwash. The main advantage a tradesman has is speed gained from experience, plus better optimised tools. Mr DIY will take a lot longer to do the same job as Mr Tradesman, but there's no reason why a DIYer can't achieve results that are just as good, and sometimes better. After all, if you are your own customer, you've got a big incentive to get it right first time. If you do a shoddy DIY repair or installing job, you're just cheating yourself.