right time for big mortgage

Hi, We sold our house a year ago,and made about 170k on the deal.We moved in with in-laws and have been saving along the way while we looked for a site to build.We found a site with outline p.p and no local needs restrictions.Cost of site was € 162k inc. stamp duty.
We applied for and were granted full planning but to date there are no contracts signed due to delays from vendor's solicitor.
We earn 70k between us and have been given a mortgage of 300k to build and kit out.(we hope not to use all of it).
We are due to close in the next couple of weeks and I am very worried at going from a position of having a nest egg to fall back on if either of us were to lose our jobs (unlikely at moment) or some other unforseen circumstance to a position of being stretched to the limit if we go ahead and in deep trouble if anything were to happen to either of us.
Mrs H. is an eternal optimist and takes the "we will always get by approach" and also points to the money we have outlaid for planning etc. so far and also that a site like this is unlikely to come again.
Any advice greatly appreciated

look mortgage payment protection mate and also salary protection as well


kk

Do you have any children? In the event of that, can you afford the 300k mortgage as you will either have (a) childcare costs on top of the mortgage payments or (b) one parent will stay at home to mind small children. It's a very different world on one income, with kids than double income no kids.
There is also a psychological shift of course, going from a position of having a lot of lovely lolly in the bank to a position of owing a lot of lolly to the bank.