I have tried to do that a number of times, but without including Hooded Crow. The one that usually fails me on such occassions is Jay.
I wouldn't have got jay if I didn't go looking for red squirrel - I saw both at The Dingle NR in Llangefni. There are now 2-3 apparently permanent resident Hoodies around the retail park in Holyhead, presumably originating from the Irish population. They're pleasingly close to South Stack, which is exceptionally reliable for raven and chough, so the three 'harder' British crows in as little as half an hour is definitely possible!
Were the Black Guillemots in Holyhead Harbour again, end of 'Turkey-something' road?
I failed with them here as I didn't know exactly where to look.
The best place for Black Guillemot is around Holyhead marina (LL65 1YA) - there were at least four birds there on this occasion. I also had one at Point Lynas and one at Moelfre. They turn up pretty much anywhere around Anglesey and the Menai Strait coast of Gywnedd, but the marina is by far the most reliable. I've tried Turkey Shore Road before without luck, but I know they are seen there.