Yup, this, really - it’s very common for vowels to shift towards ‘a’ in the north - paned becomes panad, and so on - dod -> dad sounds wrong (probably because it’s an existing word), so it ends up ‘dwad’ - but it’s still just a shift on the pronounciation scale… 
And really glad you enjoyed the book…
“dŵad” is a variation of ‘dod’ and was used in the Northern version of the BBC’s Big Welsh Challenge.
My Carmarthen grandfather used to pour his tea into his saucer and drink it from there. I don’t think that my grandmother entirely approved.
Sue
I’m sure I’ve read that that was what saucers were for originally - one poured off one’s tea to cool slightly, and drank from there. So probably more old-fashioned than uncouth!
My Nana used to pour some of her tea into the saucer and let me drink it. My Stepfather used to do the same and give it to the dogs!
Quite so! 
A-ha! With that explanation, I can correctly hear the pronunciation shift in my head as well as replicate it verbally.
Thanks. I’m a Welshman myself mind, live here still.
With a slurp, I hope.
No, I’ll bet she gave him merry hell when the visitors had gone.
As I read the GPC entry http://geiriadur.ac.uk/gpc/gpc.html?dyfod , the original word was dyfod (thus dyfodol “future” is that which will come, in the same way that gorffennol “past” is that which has finished, gorffen).
That then got simplified dyfod > dywod > dywad > dŵad in some regions, dyfod > dywod > dowod > dod in others.
Yes, I never saw my grandfather drinking tea from a cup, even though my grandmother always served it to him in a cup and saucer. He would pour a little from the cup into the saucer and enjoy it from there. This was in the mid-Fifties in Gelli, Rhondda Valley.
Originally cups didn’t have handles and were just open bowls. I’m not sure when saucers were first used under cups. The original use was to hold sauce!!!
I used to think this, but I have friends from Pembrokeshire and Llanelli (both first language) and they both say paned. They say they don’t use disgled.
My “Bamp” used to pour his tea into his saucer too.
I read (or heard) somewhere, possibly here?, that there was some link between a discus and a saucer, and then the disgled, which was a sort of paned to go with it.
Maybe I shall stick to paned then, in honour of my Pembrokeshire ancestors.
Sue
Could also be an age thing as well - these things cam evolve. It was always disglyd in my mum’s family when growing up, but I’d never heard paned or panad and i doubt they had much, if at all either. With more contact, school and media then that can alter things over time perhaps.?
You are more than welcome to stick to your disglyd in our Oxford meetups, as far as I’m concerned.
But I was wondering where it actually comes from. I mean, “paned” or “panad” is fairly obviously derived from cwpanaid. But where does “dysglyd” (and variants) come from? I’m not finding it in dictionaries.
However, I noticed that http://geiriaduracademi.org gives dysgl for “dish”, pronounced “dishgil” in the south…
I know that’s not “disglyd” or “dishglyd” or “dishgled”, but it’s not that far off, is it?
(anyone else have suggestions for its derivation?)
For what it’s worth, when I was in southern Bootcamp, we visited a school. I forget where exactly, but it would be in Ceredigion somewhere, and a young teacher happened to mention to me that he used “dishgled”, and implied that that was the common usage there. Admittedly, that’s not very near Pembrokeshire.
Disgled does indeed come from disgl - the ed on the end indicates it contains something. Panad/paned comes from cwpaned and is a cup of whatever whereas cwpan is just the cup. Similarly, a glass is gwydr and a glass full of something is gwydred.
I suspect @Toffidil is right here. Is probably annage thing. I suspect your ancestors would have said disgled.
Thanks Siaron. From http://geiriaduracademi.org, I would interpolate that “cwpaned” and “cwpanaid” are just alternative spellings for the same word, or rather, the Sunday best spelling is “cwpanaid”, but it’s pronounced “cwpaned”. See the entry for “cupful” -> (Southern): “disglaid” (pronounced “dishgled”).
(But we know these supposed north/south distinctions are approximations, at best).