While I do appreciate the offers of help in building the family tree, I'm just not sure I am comfortable with complete strangers having access to my DNA profile.
I too feel for you in this dilemma & having to deal with it as it can't be easy, given the circumstances of finding out but I wish you luck in finding your roots.
You don't need to give access to your DNA details.
You can send the info. from the trees you've viewed to Heb66 or if they're public trees then a link to them & take it from there?
543 cMs is definitely one of the highest I've seen for an unknown relation & well worth investigating even if it involves help which can be worked out.
It would be worthwhile checking out reasons for an Irishman being in your town/county at the time of your conception.
I'm sure you said you were 40 yrs i.e. 1979-80 depending on when you were born.
What industries were on the go, were there any Army/Navy/RAF sites, any fishing ports & try to link up what the possibilities were from the area in Ireland your matches lived.
It could've been something simple e.g. a friend's smoker/wedding/funeral or holiday?
It would be worth asking those questions of your matches as it may get them searching deeper out of curiosity alone?
Annie
Add...I forgot to mention, is there any of your mother's friends of that era still living who may be able to give you some info?
It's amazing how little snippets can form a wider picture!