Thanks for your replies.
@BuzzThat make sense, it's a fairly simple design.
@PeterStarck you're right about services, we need a pumping station to lift approximately 1m for sewerage. Electric is in at 9k, water is quoted at less than 1k though.
@SteamyTea our plans are all approved with no complex conditions, just waiting for building regs approval so hopefully professional fees should be limited.
The design is fairly simple with timber frame quotes between 55 and 70k depending on the level of insulation and company.
@Triassic sounds like you're doing well.
Our plant room is centralish on the south side wall to ensure short run for ashp and mvhr. Could you recommend a brand or company for either of these?
@PeterW so far we have found it very useful it is to be available to solve problems early to reduce wasted time when we're paying for skilled labour.
Here it's difficult to find anyone you'd want near your house for £330/week.
My husband doesn't earn a massive wage and both of us want to be hands on anyway, we'll probably only do this once!