Hi Hoops,
The main thing I would advise is for you to decide on your first preference of area or number of areas you would like to live in and have a good look at properties both on the open market and within the AH schemes within whichever Local Authority they fall. Have you talked to the housing departments within either to enquire how both schemes are now progressing or if the proposed rent to buy schemes are close to getting off the ground? If the amount you have been approved for by DCC isn't sufficient to meet the prices the market is still demanding in that area AH may be your best bet if that ends up being where you really want to live. Likewise if Fingal is where you would prefer to live have a look at what is on offer there under AH, I know SDCC had an office in the Town Hall in Tallaght where they had details of their schemes, maybe both Fingal and DCC have the same?
Many people have experienced problems with both Shared Ownership (due to the high repayments as rent and a high variable mortgage are both charged along with increased equity) and AH (due to valuations recently) enquire as best you can on the net or through friends how the particular scheme has operated if and when you find somewhere you may be interested in buying.
Have you applied for a mortgage on your own as yet to see if you can purchase without needing to go either route?
Best of luck
.