I am something of a "cockney sparra" having been born and bred in London some 50 plus years ago... so I'm used to folk "taking the mickey" out of my way of speaking where ever I go... I don't use full-on rhyming slang much, like my Gran used to all the time, but little bits creep in now and again, words like "titfer" (tit for tat) for hat... or apples (and pears) for stairs... "mutton" (jeff) for deaf... and that sort of thing, they just sort of slip out and find their way into what I'm saying without me even thinking too long and hard about it. It just "comes naturally".
Mind you, having said that, nowadays it's more like ghetto slang like "My cribs' in Lun-dun, innit?"

so the whole thing has been made into a form of oral shorthand really... and altered beyond recognition in a lot of respects, which in turn has made me interested in all dialects for all of my life really.
I spent my youth traveling much of the UK, my family were fun fair working nomads... and I'm pretty good at hearing somebody speak and then guessing where they come from as a rule. I can certainly tell a Yorkshire man from a Kent one in just one or two brief sentences... quicker than that if they are Essex or Hertfordshire... or Cambridge or Norfolk for example... I don't think it's just on the sound of the words, either, it's something in the mannerisms they apply, maybe, and the energies they give off that I'm picking up on too perhaps...
In fact, I find myself getting a bit "put out" if I can't quite place it because I like to challenge myself (as sad as that might make me sound)
I've been visiting South West Wales regularly for the last 30 years, having fallen in love with it back in 1975, and been honoured to have been living here (Pembrokeshire) for the last 3. I have just learned about the Landsker line, and what the locals refer to as “Little England Beyond Wales.” There's certainly not much Welsh being spoken (in public) where I am, the road signs and other ones like sign posts for churches, schools, train stations and so on are in English first, and Welsh second. Where I am there's a busy ferry port close by to and from Ireland, (sailings are twice a day every day) so quite a few of the locals have Irish (or Irish/Welsh now) accents.

The two blended together are something of a curious mix... I have to say

Sort of "top o' the morning to ya" meets "Croeso" or "Shwmae"...
I could listen to the Welsh speak all day and all night, even if they were just reading the telephone directory. Be they North or South. It's all so musical and enchanting. Not just the words and lilt or accent, but the spaces in between, the pace, the excitement levels, the passion, the expressions, all of it... it's just wonderful. Even English spoken with the slight Welsh accent sounds beautiful to me. And I like to think I'm starting to pick it up a bit now myself too... when ever I speak to my friend who's still in London she says I sound more Welsh each time

My next door neighbour is from "oop north" but he's been in Wales since 1942, and clearly has taken on lots of the Welsh dialect, so his voice is very interesting!!! (sort of "eh by gum, there's trouble with me whippets" meets "borra da")

- please excuse the sweeping generalizations and blatant and perhaps unforgivable stereotyping, but I think you'll get what I'm trying to say... No offense meant by it at all. All said with honest affection and as terms of endearment, I can assure you.
I have noticed subtle differences from those in, say, Barry Island, those in Bridgend, those in Cardiff Bay, those in Swansea and so on... nothing I can really identify but tiny influences making minute changes... enough to just notice if you pay full attention... I found Carmarthen accents sound quite different, more like the North ones really. The more I visit the town there, the more this is becomming clear to me... and I've been spending a fair amount of time in Cardigan too lately, given that's where I'm getting some of my harp lessons now, and I've noticed it's slightly different there again.
I had to laugh when I heard the phrase "where to you from, boy?" and "I'll be there now in a minute" (otherwize known as "the Pembrokeshire Promise" - like "Manyana" but even slower...

I believe the Cornish call it dreckly...
Listening to somebody from Anglesea speaking in Swansea quite recently (Kris Hughes - MonDruid) I have to confess I was struggling a little bit (to keep up) and in awe / somewhat star struck
When the Welsh speak of place names I can't quite put a picture in my mind of where it is they mean and then I feel "lost" because the way it's written doesn't sound in my head when I read it like how it's heard in my ears when it's being spoken. That aside, the talk was totally amazing, both for historical content, and for how it "came across". Just love the Anglesea accent, I does. (See what I did there?

this is a welsh way of putting things...!)
I hope it will get easier with time and more effort on learning the language on my part.

I certainly look forward to it. I'm finding lots of the posts on here very helpful in that respect so thanks to all who have contributed.