I can finally update this now. It's been a long process but I've got tenants moving in and I hope it's been worth it. I ended up getting a place that didn't need renovating - just decorating. Still, I've learned a lot.
Firstly: fucking hell, painting was more difficult than I imagined. I learned the hard way about buying cheap paint for the living room and had to do it again with better stuff.
DIY. I am awful at DIY; it's truly embarrassing. If you don't know what you're doing, then hire a professional - that's my key takeaway. I decided not to risk killing myself wiring in a light feature, and I also fucked the laminate flooring by trying to do it myself and had to bring someone else in. Also, the only honorable tradesmen on Earth are Henda, Tapeworm, and the guy who replaced my window frame. All the others can get shoved in a gas chamber. Holy fuck, there's some rip-off merchants out there.
Some good aspects of it are how I've managed to decorate it. I went totally overboard but it looks like a show-home. The leasing agent was practically wanking when he saw it and it's been advertised as 'visually stunning'. I'd put photos up but I don't want some fag to dox me and send trannies to my door. I stuck coving up, a bronze curtain pole with amazing curtains, bronze chandelier, ornate artwork, candles, vases, etc. I really love how it looks and I had a lot of success using Gumtree (UK Craigslist) to pick up some really fancy items for cheap. I searched the expensive areas for rich people who were moving out and managed to pick up some awesome bargains (e.g. mint condition IKEA TV unit for £20. Marble table worth 2 grand from an old man who couldn't move it).
It feels like a nice milestone now after burning myself out by going at everything full-on for so long. Neither of my parents even owned a house and now I've got something I can leave to my nephew one day. Feels good. It's also bringing in just under £600 a month now, after leasing agent fees are paid. I'm not sure I'd want to do it again with another property, though.