The white isn't really a plastic. It's a super durable material that will give you long performance and I recommend it over the metal. I would only use the metal in an industrial/commercial type of location. You are very welcome!

White is a classic option when you have other competing colours in the space, otherwise aqua shades will work beautifully with both the cream & brass bed and the grey walls and flooring.

I believe that you can paint acrylic based paints over oil based paints as long as you use the appropriate sealer/undercost in between these two paint types, The people that sell you the paint will be able to assist on this, as well as Dulux/Truman’s websites. I did this at my home and it come up very well. In this case, 60 year old in built wardrobes were changed from mauve to natural white. I agree with the logic of what big reader is saying. From what I can remember, natural white already has some yellow/ochre in it, so the variation would be less noticeable.

I would paint the trim the same colour as the walls. The skirting and architraves are not substantial and don’t need to be a contrasting colour. I also think Vivid White is harsh against your floorboards and current floor coverings. Have a look at some of the Three Birds Renovating houses. They and others use the same white - wall, ceiling and trims. It’s is a much more up to date way of doing it. If you go this way you may find Antique White USA, which is generally a colour I like, too creamy.