Hi,
Mae’n - I’ve heard this pronounced ‘man’ and ‘my’n’ in the lessons on Level 1…Mae’n ddiddorol (sounds like man diddorol and mae’n bwysig sounds like my’ n bwysig.
Is this just me? Or does the Mae sound change depending on what follows it?
South Wales version.
Diolch i chi!
Ian
It does change, but not because of what comes before or after it - it’s just a case of different dialects. Use whichever pronounciation you feel most comfortable with and keep the other in mind for when you hear others use it.
In the South, the “ae” sound is often pronounced as a long “a” as in “bard”.
Examples:- traed (feet) pronounced traad; traeth (beach) pronounced traath; and, most notably, Cymraeg (Welsh) pronounced Cymraag.
North Walians also have their own variations. “Eisiau” becoming “isho” to name but one.
Variation in pronunciation is not confined to Welsh, of course - my Derbyshire wife and I often need interpereters when talking our versions of English. - eg “bus” versus “booss” 
Edit - beat me to it, Siaron
In big parts of Carmarthenshire/Ceredigion there is a tendency to pronounce the “ae” sound as more of a “aa” sound. Cymr-ae-g becomes Cymr-aaa-g and so on.
This is very true with Mae’n as well, which you may sometimes hear as closer to “Man”.
If you’re doing the Southern course, you will bump into this a few lessons down the road when you come across something like “Mae isie i fi”, which will be pronounced like “Ma isie i fi”.
Don’t worry about it, roll with the punches - and your language/accent will develop with your own personal taste and those around you.
Best of luck with your Welsh journey.
Diolch pawb
Is the same true of the varying pronunciation of ‘deall’? Iestyn and Cat seem to say it differently, so I’ve assumed I can go with either…
And thanks for your question @IanWills - I’d wondered too
Yes Ann, it’s the same with deall - and with lots of other words too! We tend not to notice it so much when it happens in our first language, but when we’re learning we tend to jump on these differences 
. As you hear even more and more accents and dialects, you will no doubt come across other variations, but now you’re forewarned it shouldn’t be so much of a problem 