About your question about sourcing some of your own internal fittings. It is best you discuss this with the builder early on. Usually, the builder's contract will specify an allowance for particular fixtures. However, some may specify actual brand and model of fittings ie taps, toilets, sinks, etc in their quote, and they may or may not allow you to vary this. IF you are happy with those specified fixtures and you think the allowance amount is reasonable, then you can go with it. Otherwise, any changes or variances need to be discussed with builder, and it is very important this be discussed upfront and before any contract is signed. Some building contracts may also disallow some variances. In any event, carefully read the contract so you completely understand what you are agreeing to, and discuss any and all parts where you are not in agreement so these issues can be ironed out. Also, and this is my own experience and opinion, but I advise specifying in the contract the completion date AND if the build is not completed on time then what happens (consider that you may be paying interest on your mortgage, be financing a bridging mortgage, etc. and/or you may also have already sold your home and then have to pay rent until the build is finished). If you are in agreement with builder to source some of the internal fittings yourself, there are any number of suppliers and sources to investigate, and this might be a good way to keep your budget in check. There will be Houzzers who are experienced at this and can provide you with ideas. Just keep in mind that you will have to have all fittings READY and ON SITE when the tradesmen require them, otherwise you will be holding up the build and that is going to cost YOU money.

This is a very relevant question for us right now as we also have to decide between clear anodised and silver coated. I was surprised to find the anodised more expensive but to me it does look entirely different. The manufacturer said one of the reasons it is more expensive is because if the anodised is scratched during manufacture, shipping or installation, it must be replaced. Whereas the powder coated option can just be touched up with a bit of paint. I'll attach a photo of my two options. Anodised is on the left, coated on the right. Interested in your responses and decision! Good luck.

The psychology within your home will be more affected by being in an environment you like and feel comfortable with rather than someone elses thoughts. It's really a style choice - do you want a softer look - consider your furnishing styles and preferences. The darker options are good for crisp and contemporary such as in full height multi paned steel Criffal windows. Try Google and Houzz for pictures. A good compromise is silver pearl which is soft but also contemporary.

It's always been a bit of a no-no to mix wood with aluminium, however I totally get what you are saying about the pros of using aluminium upstairs. I personally would have gone totally one or the other, only because it bugs me when I go to a house and there is a mixture of window types. I would only do it if it was very difficult to tell them apart ... I know that they can make aluminium now so that it is the exact width of the wooden windows so has the same visual effect.