As others have said, AnnieJ only you will know if you have made the right decision, although you must have weighed up all the pros and cons first? Perhaps you have personal reasons that need you to be close to your family, or that your family need you closer for their own peace of mind, especially if you’re moving a long way?
A new build will be so much warmer and cheaper to run than it’s older equivalent - I often think DD1 has the heating on, and I’m surprised to find that she hasn’t - so well insulated.
Your house should come with the NHBC guarantee and I assume that a mortgage isn’t necessary, in which case, personally, I wouldn’t bother with a survey at all. A snagging check, which is just those annoying little things, should be done between you and the sales agent prior to handover and the team working on site should rectify things. Once you move into the house, should you find further jobs, e.g. a scratch on a window pane that was previously missed (or is new) that you would like replaced, it is essential you move quickly, as there will be time limits, but the builders customer care manager should be able to help you out.
I can understand your feelings of uncertainty. We have a respected poster gMattie who is in the throes of a move and has had a bit of a rollercoaster ride, but is nearly there.