I've always been confused over the loo/left-tenent thing so I really cant help you there lol.
It's not the same all over the UK, in fact its not same for every word in Wales, but in Welsh we have a completely different alphabet and some letters are actually made up of two letters put together (e.g. Rh, Ll, Ch, Dd) and are pronounced slightly or even completely differently to how you would say them for an English word. I found this about Ll (I've put the most important part in bold):
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1.1. Ll
Ll has an undeserved reputation for being difficult. In fact, it's by far the easiest of the non-English letters to learn. The problem is that it is often advertised as an "unvoiced L", and that's not quite true.
- Say the English word antler, making sure you say the t as a real t, not as a glottal stop. That is, make sure the tip of your tongue is touching the back of your upper teeth or the ridge immediately behind them.
- Drop the an part and say tler without using your vocal chords. In other words, whisper.
- While saying this, try to sustain (hold) the l as long as possible. It should sound a little like air hissing out of a bicycle tire. That's the ll sound in Welsh.
If that doesn't work, try a similar technique using the word please.
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I wouldnt recommend trying it unless someone in Llangollen teaches you know as its quite hard to understand until you hear someone say it/explain it properly. I don't speak fluent Welsh but I know enough to understand pronunciation and I still struggle with it in some words
