One hospital can be upgraded to a large hospital for every 3 hospitals you own.
I'm trying to play realistically. Realistically, there's almost no hospital that doesn't have a paeds ED capacity, an intensive care unit or maternity services (depending on how rapidly the CQC close them down). In trying to replicate this, I've rapidly run out of large hospital allowance.
Are there any cons to building several hundred hospitals on, say, Antarctica to increase the number of large hospitals I can have?