Hi all,
A good sound cost plan is the best way to start, this should be based on up-to-date figures (generally the latest edition of a SPONS building price book would be sufficient). This would give a good understanding of the areas in which your money would be spent. This can then be modified based on your required kitchen spend, AV, lighting etc.
Don't forget this should be a working document throughout your build and can be further broken down with a Bill of Quantities. This can assist with material and labour pricing and budgeting.
If you would like an approximate m2 / sqft rate then please shoot me a message.
Thanks,
TheQSguy