Your parents could gift you the site for no value on the declaration that it be used to build your own private family residence, thereby attracting no CGT. In terms of stamp duty the rate will be 0.5%(Half normal Value) of the market value, as it is a transaction between related parties.
You can gift €50,815(47,815 + 3,000 exemption) tax free to your parents as stated below:
A threshold of 47,815 euro applies to gifts/inheritances made by a person to his/her parent, brother, sister, niece, nephew, or grandchild. In certain circumstances, a parent taking an inheritance from a child can qualify for the 478,155 threshold.
Somebody else may be able to clarify if you could gift 47,815 to each parent. You can always gift €3,000 (annual exemption)each year to them tax free which may also suit.
May not suit you, but its an option at least.