I used to shore fish around Angelsey many moons ago...As far is i can remember there are boats chartering out of Amlwch, Benlech, Trearder Bay and obviously Holyhead..Im sure there must be more...Beaumaris comes to mind too n im sure there is a good tackle shop there..Just remember Angelsey is only small so even if the boat you fancy is across the island its never very far..If you fancy a go at shore fishing Rhosneigr itself has one of the best beaches around and Cable Bay just up the road has some fantastic rock marks giving easy access to deep water..
ps..i apologise to all about my dodgy welsh spellings..i never did get my head round it.
pps..get a copy of sea angler n look in the classified at the back..