Hi, I've done Caernarfon - Weston (and back, and back again - thats another story...) and also Weston-Isle of Man - Teesside.
Out of caernarfon climbed to 5000' on a direct track for either Killiney or Bray south of Dublin. Wx was fine, apart from a big lump of status 1000' - 4500'.
Speak to Valley or London Mil via london info and see if the danger areas are cold or not. If cold just route direct, if not you'd have have to go further north.
Dublin CTR has VFR routes, controllers all very helpful, but expect a LOT of freq changes as you have to speak to dublin mil bases for clearence and back to dublin again.
If wx is a bit dodgy they may say "Can you see those two big red towers ?"
"Affirm"
"Well just fly towards 'dose 'den." :-)
The two big red towers are at the mouth of the river liffey.
The next day we went Weston - IOM. Again lots of freq changes, but the controllers v.helpful, and basically vectored us around to the north of dublin, coasting out and picked up a radial to IOM ibd.
Hope this helps.