Wet underfloor heating is fantastic (esp when combined with a heat pump - sure that would be OK in Scotland)
Electric UFH is quite expensive to run
Remember one of the largest costs is conecting to servicese (phone sewage, water, gas & elec)
There are some great magazines out there and some great plot finding website - but you do need to pay
Remember you can reclaim the VAT on a new build - so keep your receipts
Will you project manage yourselves?
Where will you live while you build?
How will you support yourselves while DH changes his job?
As you can tell I'd love to do this
Have you thought about solar panels?