Leaving aside the issue of the transfer into your mums name for now, there is an exemption currently where a parent transfers a site into a childs name for the purpose of building their principal private residence, the site is worth less than 254000 and it is the first such transfer- the exemption is from stamp duty and CGT. There are other conditions, and you can check these on the revenue website or with your solicitor. If the above applies to you, its likely you will benefit from the exemption.
In relation to the divorce settlement, I think this would have little bearing for numerous reasons.