Have a look here, which should tell you all that you need to know.
http://dublinpilot.bizhat.com/Flying_in_Ireland.htm
The usual route to Weston is KLY NDB, "Pigon House Chimneys", then follow the river Liffey to "Palmerstown Roundabout" sometimes called "Toll Bridge" by ATC. From there you'll be visual with Weston. Usualy clearance over the city is not above 1500ft or sometimes not above 1700ft
My top tip is to make sure you are nice and high when you contact Dublin ATC. If you contact them when you are at 2000ft-3000ft they will ask you to desend when you are way out to sea. If you are at FL60+ when you contact them, they usually let you stay up there for a bit longer! I've never really understood why, but that's the way that it seems to work.
dp