I think you should consider houssaon's idea of painting it the same color as the walls. Is the top of the tv console painted wood or is it a stone or composite? In the pictures my ipad shows me speckles (not dirt!!). My ipad sometimes *lies* to me. :) If the gray is the prominent color in the paint, maybe a darker gray would be a good choice too. If you are happy with the gray/green color next to your bookcases, then you should be able to pick a gray that would look good with both the new paint, and the bookcase. Gray next to the fireplace shouldn't be a problem :)

Paint the wood floor with a flooring paint. If you want to be creative, you can create your own special design. I've had painted wood floors in a previous home and everyone loved them. If you get tired of it, paint them a different color! Saves doing rip out and better for the environment! My floors held up well. I was surprised. I even did a faux marble floor for fun.

Slipper Satin, Stoney Ground or shaded white are the recommended complimentary colours but if you really want a grey you could try strong white. I've got French Gray Units which isn't a million miles away from Mizzle and I've used Dulux Egyptian Cotton on the walls, it's definitely grey (although doesn't look it on colour chart) but got a beige undertone so would work with your flooring.

I think maybe a mid grey would look good...especially if you chose one with green undertones to tie into the kitchen etc. It's also more maintenance friendly than white or cream...which get dirty very fast. You can see the kind of colour I mean in this picture...but if you feel the colour doesn't work on the inside you can always have a different one to the exterior!!