The OS map uses 'Ysbyty' and as this is indeed the correct Welsh spelling for 'hospital' I've changed the main spelling to this. It wouldn't be the first spelling anomaly in the Modern Antiquarian book. Thanks for pointing this out.
...is notorious for regional variations. Not to mention if you compare a recent OS map with one say only 50 years old there will be many changes. Compare again with say a late 1800s map and most of the spelling is Anglicised.