> Being a DIY type, I was appalled at the building standards

Yup. It's no understatement to say a good tradesperson is extremely difficult to find. They all charge the inflated going rate regardless of their skill level, as people are desperate. They often get pretty shiry/nasty if you demand things or want to check their work - to keep you afraid and to accept their very subpar work.

Materials are shockingly terrible across the board too

I've been putting off renovations because I've had so, so many bad experiences with tradespeople in the past.