When I think of French country, I think of blues & yellows. Paint the rooms pale blue & yellow with white furniture. I'm sorry, but I don't know what the Annie Sloan treatment is.
I really love when shelves & dressers are built into the sloped walls if you have room for that. I added the pink room because it has beams like yours. Bright paint & that oversized artwork make it look very cheerful.

Do you have space for a window seat in the room with the end window?

I like your idea of a window seat but the window goes right down to the floor, so not sure that it could work unless we did something either side of the window.

Try a simple bench there similar to one of these. Add a cushioned seat. They wouldn't block much of the view since you could see over & under it.

Pastel is the new gray I hear. :) How about painting the rooms a soft pastel color of your choice for each room. Even though the color will be different the pastel theme will keep the rooms looking cohesive. Inspiration:

Before committing to any furniture I would do a lot of research on storage options. e.g. you can get beds which have drawers underneath. The furniture needs to be light to make the room feel more spacious. if the furniture is similar color to the walls it recedes into the wall. You want to see as much of the floor as possible so get furniture which is elevated off the ground and lets you see the floor underneath, e.g. you can have floating shelves on the walls for books and nick nacks

ps invest in some HUGE MIRRORS

What a dream house! Congratulations.If wanting to keep close to original and the age of the house, I would suggest different shades of white. I wouldn't think there was much saturated colour then, probably just what we would call today antique white. and lighter colours would make the spaces light & airy.

Thanks for the paint ideas. You're absolutely right about shades of white/ grey and pastel colours. They are in keeping with the age and style of the house. I want a very muted, paint palette so that the wealth of original features take centre stage. Very helpful advice about furniture styles and allowing lots of flor to show. I'm planning to furnish with old French pieces picked up at country markets and sales. These almost always have legs, so the floor will always be visible.. Do you think I should paint the floorboards a light colour too, maybe a string or ivory toned white?

Keep all floorboards natural (pine, isn't it?) and first start by sanding/stripping these beams. Give all the old woodwork a clear coat, but anything new offwhite (like the windows).

Check out the material on the blackened wood, if it's tar, keep them black.
Personally, I'd go for offwhites, but pastels or even earthy greys could look lovely. Not too much color, make it calm and serene.

I have to admit, I really like the off white with the beams in the photos above. Very simple, but beautiful.

I think I would add some color in the bedding through. You don't need much. I like the pastels that Darzy showed. Unfortunately your rooms aren't as big as the ones in the pictures so it will be more difficult to make them look as light and airy as those. Since you probably can't put up curtains on the windows, try creating a canopy over the beds to bring some fabric up like the El Aguilon photo above. You can even use simple white sheers.


https://www.houzz.com/photos/2009-southern-accents-showhome-traditional-kids-dallas-phvw-vp~505315

There's so many ways to make a canopy. Here's more.

Light colors (your intent to de-emphasize the wood beam's contrast is good), less clutter (fewer but higher quality furnishings), clear traffic and vision lines (draw the eye through the space), horizontal patterns over vertical, spot/task lighting and activity areas (create visual niches, not actual, chopped-up sections). Embrace the comfort and security (bookshelves, reading area, a table full of plants under a skylight.

If you're are romantically inclined, you probably won't need to refinish any antiques - save the patina and use them as they are. In the states we call it Shabby Chic, but the French have used it for decades without having to put a label on it. Pastels will be wonderful.

So many good ideas coming from all of you. Thank you so much. Would never have thought about horizontal versus vertical patterns but can now see it makes so much sense. The house was originally the lodging house for the local abbey and was maintained by the monks as a guest house for travellers. So whilst we don't want to return to monastic minimalism we do want to keep everything fairly plain and In Keeping with the age and style of the house. Will be going for the shabby chic look but in a pared down way, plain or striped rustic linen fabrics rather than florals, no unnecessary clutter, a few good, aged pieces of furniture which were painted years ago and are showing their life history, plain wooden French sleigh beds with lots of old white linens . No bright colours but muted slightly muddy pastels. Have found your pictures and suggestions a real inspiration. Thanks again.

Be sure to post pictures as you make the changes. It's so nice to see the improvements people make when they actually post pictures of their progress. Good luck & have fun!