This is a difficult question to answer and one that gets asked a lot. I will try and give you some really clear rules of thumb that will help you get an outline financial plan in place so you can start an effective conversation with an architect or builder. You will find that some builds will be cheaper and some will be more than the rates shown below.
With these figures, you also have to take into account that inflation is continually pushing up prices , and material costs are constantly fluxing (Covid closing factories, droughts affecting timber supplies, wars in countries producing materials). A good architect will more than pay for themselves in this situation by being able to steer you towards building materials and methods that are currently affordable at the time of your project.
There are also other site-specific issues that affect your cost, these can include listed buildings, difficult to access sites, high number of trees, just to name a very few.
The build costs below are ball-park figures as of September 2022 and may become out of date fairly rapidly for the UK, but you have to start with something. We have achieved projects better than these rates, but it is preferable to be a pessimist when budgeting with property. We can take many steps to predict the build cost, but the final price is only known once a builder or contractor has provided one for the project. And before that happens you have to design it (You see we are in a Chicken and Egg situation here).
So lets assume we are building a 3 bedroom two story family house which is about 160sqm:
We use these figures:
£1500/sqm -£2000/sqm : Very Basic (Often Self Build)
£2000-£3000/sqm : Complete build ( Basic finishes up to Good)
£3500+/sqm : Deluxe!
So for your 3 bedroom house. We end up with these approximate build costs:
£240,000- £320,000 : Very Basic
£320,000 - £480,000 : Complete Build (Basic - Good)
£560,000+ : Deluxe!
We can of course explore all sorts of innovative solutions to get a different cost. You can look at Offsite Modular Construction; Construction Management Contracts; Self Build; felling your own trees for timber on your land; repurposing existing buildings, the list is endless. But this sort of conversation needs to be had with a construction professional face to face. And if you want to get ahead of everyone else, and do it better, do it faster and do it cheaper and do it your way, well you are just going to have to innovate and think hard!