I guess for non-translated town names, we all tend to use our own first language phonetics, or improvise on what we think could be appropriate.
But since we’re talking of the UK, here…I believe you can’t ignore the fact that there’s no way to guess how to pronounce names of towns in English - cause they’re totally random!
Therefore we (foreigners) pronounce many of them wrong - unless we happen to visit them or have some connection to that place.
Does anybody really worry about it, over there?
And if you think about it, with Welsh a few sounds may be a a bit complicated to get right, but at least phonetics is consistent!
I think you’re on to something with the phrase “non-translated names”. As a Swede, I would want to pronounce Gloucester as close to the local pronunciation as possible, since we don’t have a Swedish name for that city; but Roma and Helsinki and København have different Swedish forms - translations, if you like - and I think we should keep using those names.
But as a counterpoint, I have recently learnt that in Swedish, Welsh (the language) is nowadays normally referred to as kymriska, rather than walesiska - which is definitely better, both for being based on how the language refers to itself, and for ease of pronounciation!
Interesting. Although I love Welsh, rightly or wrongly, possibly due to convention, I find myself using the place names and/or pronunciation relevant to the person who is listening to me.
Strangely, this tends to vary, depending on where I am and the language that I am speaking at the time. So locally I’d probably say “Lanwern” and “Lanercost”, but Llanelli. I was going to include Munchen, but it seems that it should be Minge - Is that right, @Hendrik?
Anyway, Is Gwynedd asking the National Park body to call itself Parc Genedlaethol Eryri (in full), or Eryri National Park?..or neither
@JohnYoung - to pronounce München (with the Umlaut - two dots - over the u) you can say the English word “munch” as in eating but try to replace the “ch” sound by the “ch” in the Scottish word “loch”, followed by “en” as in “enclose” - Munch-en. The result is not perfect, but in English we do not really have exactly the same sound as the Geman “ü”.
It’s always next to impossible trying to represent the pronunciation of a word by the means of another language, because as you rightly say, there is no way to represent ü in English. But the bigger problem here is that the ch in München doesn’t sound like ch in loch. It is closer to sh as in Welsh, stwnsh or hansh. So I’d propose a closer approximation through a Welsh pronunciation of “mynshen”.
If most English people have figured out how to read and pronounce Worcestershire…I’m sure they’re perfectly capable of pronouncing Eryri and/or Yr Wyddfa if they want!
It’s strange how tricky " PARC CENEDLAETHOL ERYRI can be to start with and then yet so easy once you’ve grasped it. A bit like Llanelli and Cymllynfell. Not as bad as Myfyriwr (male student), though.
So I’ve been saying Y Wyddfa in the (wrong) Hwntw/Southern way Ah well hopefully people thought I meant the meeting (yr Oedfa)
A useful link here for pronunciation of place names - just click on the places marked on the map to hear the (a?) pronunciation and see the name: https://www.mapiau.cymru/mapiau/MapLlais/index.html
… unfortunately, except for Yr Wyddfa
Yr Wyddfa is a lovely name for a mountain and I delight in using it, the same as I delight in using Pen llithrig-y-wrach, I suppose because, for the latter, there isn’t an alternative. The problem in trying to make Yr Wyddfa the default name for Snowdon is that it would just give non Welsh visitors the chance to enjoy pronouncing yet another name incorrectly. Given that a lot of non Welsh speakers variously spell Snowdon as Snowden, Snowdin or Snowdun, there is probably not much future in forcing Yr Wyddfa. There was a move some years ago to call the Snowdonia National Park, Eryri-Snowdonia but I don’t think that compromise ever really caught on either. Mind you, if it came to a compromise, what about Eiradon? How does that sound?
Yr Wyddfa, eh?
How to pronounce it? - the “wy” seems to produce two versions of pronunciation.
Have you heard non-Welsh speakers trying it??!!
Why not just have BOTH???
Anyway, it’s all a load of fuss about almost nothing, really, don’t you think??!!
I don’t ever really consider these local concerns to be a fuss over nothing because it’s obviously a contentious point for locals. So really, those of us on the periphery should make the effort to understand what the “something” is that they’re “fussing” over. If it means something to them it’s important.
hopefully they don’t start a renaming battle! 
Ah well hopefully people thought I meant the meeting (yr Oedfa) 
