Well, maybe the best advice might be not to be too worried about relatively small differences in the sounds. 
- when you’re speaking a lot of people may just think you come from a different area
There are bound to be differences between different parts of Wales (even to the extent, in parts of SW Wales, of the pronunciation of Oes as ‘Wes’ and coed as ‘cwed’ with an English ‘w’ sound ) - and there are very noticeable differences too in vowel sounds between different parts of England, although the pronounciation taught as the ‘standard’ pronunciationis from Southern England