Apart from Air B&B (heard very bad things about it & disagree with much of its approach) - can anyone recommend any good holiday rental sites/companies?

I have used Vrbo a bit for accommodation abroad, or perhaps more correctly, I have used Home Away which is the same company but was re-branded.
I have found them very good, as you tend to deal directly with the property owners, and can email requests, or ring and ask for help with transfers, update them with ETA changes etc. All of which is particularly helpful when booking flights and accommodation separately abroad.

There are a few of these companies - Homeaway, VRBO, and Expedia to name a few. I suggest you go on trip advisor to see the reviews. I’ve used Airbnb a few times and found them satisfactory.