I did mine last year and company was quite professional (contracts, invoices, everything white). I did have a couple of weeks delay on delivery, but we negotiated a 10% cut on already agreed price because of it.
Company is BOI kft, just outside budapest. They come to measure the windows prior (they don't trust owner's measurements) and then fit it. Large choice.
I have 6 windows to repalce, its a traditional apartment so they are large.. where yours similar and do you mind telling me the approx cost per window? PM me if you don't want to cost made public !!