You are right to not accept Bellway's "proposals"
It is also disgusting that, having said they will write to you (e mail or letter) it was you that needed to call them to find out what the outcome of their "meeting" was.
I agree with you, this "proposal" is just another bodge job to cover over their even worse "workmanship".
Furthermore, you have a contractual right to have your home built and to look like the working drawings.
I would escalate this to the NHBC. And to CEO Ted Ayres.
It would certainly be one for the
New Homes Ombudsman when or if it is set up by government.