Calling Holby City experts - where is Holby City set?

https://www.imdb.com/title/tt0184122/trivia has an entry "It is set in a hospital in London".

I'm 99% certain that this is not true, but I want to be certain before I delete it. As far as I am aware, Holby City is set in Holby, a fictional city in the fictional county of Wyvern. Casualty (also set in the same hospital in Holby) used to be filmed in Bristol, and a lot of very clearly recognisable Bristol locations were used until filming transferred to Cardiff. This has led to people believing that Holby is a fictional version of Bristol. Certainly Duffy (Lisa Duffin) had a strong "Brissle" (Bristol) accent in the first season, way back in 1986.

Wherever Holby is, I think the evidence is strongly against it being in or near London. Unless you know differently (to use Esther Rantzen's catchphrase in "That's Life").

I wonder if the confusion has arisen because HC is *filmed* in Elstree, north of London.