Firstly, you need to know the full dimensions of the viv, then you can plan how you are going to set it up.
Do you intend to use a substrate layer, if so, how thick.
Do you intend to put natural stone in, or cork, or branches ?(what do you want to use in the viv).
If you arent buying "kits" for the basking lamp and fixtures etc, you need to source parts.
The UV controllers/starters are complete things, and you just need to buy a bulb (no wiring etc to do). Its also advisable to buy a reflector for the bulb you get, so you get the most out of the bulb output.
You can buy "kits" to put the basking lamp in with, none are particularly great or cheap for what they are.
I did my own, at about half the price, but remember if you do this then the basking lamp will need a suitable socket (cant use plastic fittings, need ceramic/porcelain so they dont melt). Wire, plugs all pretty cheap from a diy store, you can buy ceramic/porcelain bulb sockets for a few quid.
Decide how youre gonna provide a platform (you can buy some things, again not cheapest option and also wont give biggest size either...) A lot of people look at making things out of plaster, kingspan, slate... all sorts.
I made basking areas out of natural slate tiles and also large flat rocks ive found. Eveen built platforms out of slate tiles broken up and glued together with aquarium silicon... lots of ways to do it.
Have a look in the habitat section on here.
And yes, Its unlikely you would need night time heating in ireland.