@needanewidea
Can most people in Wales say ll words properly?
I'm originally from North East Wales, and the answer is No.
Many can, because they have heard it often from an early age, but those who have had pretty much no exposure to spoken Welsh can't/won't.
When it comes to place names many residents have no idea that the village where they live has a welsh name that isn't pronounced the way they have said it all their lives. They will laugh at you when you say it the welsh way. Examples could be Bagillt, Rhuallt, and Caergwrle. (Welsh speakers do not say Bag-ult, Roo-alt and Kagurly)
When I first started work, locally, the welsh first names were mangled e.g. Huw was Hoo, Dewi was Dowey and Arwel was Ah-wul. This was in the bit of Wales we jokingly called South Merseyside, i.e Deeside.
Even Gwyn (shortened version of his first name) got his name written as Gywn. None of those names are unusual or difficult to say.
You can correct people, but generally people don't like being corrected.