there is no problem with returning to ireland once you have completed your medical degree in the uk.
After you qualify you will be provisionally registered with the GMC in the Uk or irish medical council, depending where you want to work. You need to do 1 year of supervised training as a general dogs body ( intern in Ireland, house officer in UK, same job, better hours in UK, better paid in ireland).
Then, you can apply for training positions in the field that you want.
I have worked in both systems. The paperwork is not too bad but they do require a lot of information.
All EU higher training are certified and transfer across borders. they must be regarded as equivilent to Irish training.
The irish college of general practitioners has a good guide here [broken link removed]
I would not worry about the current mess in the Uk, it will get sorted soon. I do feel sorry for the poor trainees there now, who have terrible uncertainty.
Best of luck, it is a long enough slog but worth it in the end.