Gloucestershire,
The house prices don't really reflect the grammars, as you can live anywhere, the criteria is the highest number on the test. The house prices actually reflect the comprehensives. Eg there is an amazing comp in Cheltenham and the catchment is tiny and expensive.
My kids go to Glos grammar. We live in Swindon. One of the cheapest towns in South.
The down side is that my kids travel to school. If I could do it again, I would live closer.
The biggest issue is accessible transport to school, and if you are reliant on a school bus, bear in mind that that means after school activities and friendships become hard, and one parent becomes a permanent taxi.
I know parts of Kent are the same. My neices go to a grammar which had no distance criteria. But their second choice distance was the issue, and they were borderline in terms of being close enough.
These grammars which take just the highest marks become super selective because they end up with such wide catchments. Also, unless there are enough grammars for the whole county, then they become super selective as there are not enough places.
I have 3 kids. Aged 19, 17, 14. They went to 2 very good schools.
If I had my time over again, I am not sure I would choose for them to travel, despite the good schools.