For the lime plaster I'd recommend Earthborn clay paint. We used it - two coats onto the lime and that's it (undercoat and top coat). We haven't had any problems in the seven years since. On the internal walls which were gypsum I used Dulux Trade Supermatt for the first (under) coat and Earthborn on top. That too has worked well. The Dulux product is one of the few I know that publishes an Sd figure for the paint and is cheaper than the clay paint of course.

Most of the MDF we used was pre-primed. From memory I think we used Dulux Trade products for the undercoat and top coat and primer where needed. Don't remember whether they have good eco credentials.

Also take a look at Auro Paints. I'm using their clay paint but they also sell a 'standard' emulsion. Good breathability with both, but best with the clay paint. Lovely to apply. The whole philosophy behind the products is environmental friendliness.

In our previous house we used a lot of paints from Ecos paints which now seems to be rebranded as Lakeland Paints. Worthy of a look too. The clear varnish was just amazing.