I got my septic tank from Murtaghs in Longford (
http://www.shaymurtagh.ie/). Bog standard type (aren't they all I hear you say), a simple concrete, dual chamber tank. whether you need a ST or a treatment system surely depends on your ground, and whether the percolation in the area will allow use of a simple septic tank, or require further treatment as in aerated treatment system. Percolation test at planning stage should give one a good indication of this. The CoCo will let you know for sure if they require you to install one. Most STs can be retrofitted with aerating systems anyway I think.
I also got a rain water harvesting system from same company ([broken link removed], no other ties BTW, just supplied me), and the cost of the two together was €3500 delivered. Had to install both myself, although they delivered the RWH tank into the hole I had prepared, and this is what one has to do, as they need to be dropped in using a special rig that comes with the lorry.
Installing the ST was handy enough, just stick to the requirements in the EPAs domestic watewater manual and you should be OK, but there's a bit in it re; percolation areas (tip: don't use land drainage pipe, gets clogged real easy, I bought standard 4'' sewer pipe and cut 4'' slits all along it with a angle grinder, much better job, and this was recommended to me by someone in the CoCo who deals with planning apps).
I see you were quoted 10K to get one installed, if thats the case, and you go for it, then I'm in the wrong job, and should be installing these buggers myself!!
A simple septic tank, dual chamber, delivered should cost less than 2K by my estimation, as most of the costs associated with my buy was the RWH tank, which came with submersible pump and a few other bits and bobs.
Good luck anyroad.
