Hi - I recommend speaking to Sashed. They do all sorts of windows, not just sash and are very reasonable and great quality. They only do timber windows but these are so much better than PVC (which are hideous in my humble opinion!)https://www.sashed.com

We are in the market to replace more windows than we'd like, and we want to replace them with the kind of sash windows that open both at the top and at the bottom, as we understand this allows better air circulation.

We would like PVC windows (of the kind which kinda looks like wood) for the windows  overlooking the back garden, and real wood for those overlooking the main road.

Can you think of any local installer?

Ayrton Windows seems to be recommended often, but they do wood only.
P&P Glass is the only one that comes to mind that does both.

Any other ideas? Thoughts? Recommendations? Thanks!