Yesterday I wanted to pre-order my favourite rose "Gertrude Jekyll" for my Bavarian balcony too, and by chance I found this link:
https://www.welt-der-rosen.de/adressen/dtl2.htm (you have to copy it, sorry)
"Only" for German rose gardens, but the idea of such a specialised survey is bright. There are three rose gardens in my neighbourhood which I never heard of.
So fascinating, enthusiastic (and a bit fanatic) - I would enjoy and use a list of rose gardens for England when pandemic allows me to come again.