If you wanted you could buy new deep lloyd loom style chairs..they come in all sorts of F&B colours. I wouldn't agonise too much about colour. obviously, you could go for the stone/taupe/ neutral colours but personally I would go for a soft purple/aubergine colour ( think natures colours) which would add the same depth of colour as your walls. Think a colour would mix the room up a bit. A cafe table looks gorgeous with flowers on which leaves room for a drink or magazine, & again, is a nod to the garden. magazines & books are hugely decorative & some say essential for a room. I use old books for the rooms I do & to add emphasis to the furniture I source. You can choose an interior magazine, monthly, with a cover that appeals to add seasonal change. Layer your room gradually , experiment & have fun. keep an eye out for the right lamps, shades & cushions & think big rather than twee. Oh! & essentials I didn't spot but could well be there are paintings & a mirror?!

Personally I would never have the same curtain style in mixed fabrics in the same room, The plain curtains act as a good foil against the patterned wallpaper, and as they are plain, you can easily change the walls if you get tired of the look for less expense.

There are loads of colour ways that you can jump in with that would be complementary. You just need to have a bit of a play and decide how much drama you would like at your window. You talk about cost as being a factor, and for the size of the window, I think you would find that blinds and curtains depending on your choice can come out at a similar sort of cost. Also as you have a lovely bay window, you may want to consider dressing the edges with 'decorative' curtains, that are styled, but never pulled. And then go for blinds for functionality. However - I would also consider the heating in your house. As a general rule, curtains retain more heat than blinds. If you want to discuss colours etc further, I'd be more than happy to have a chat. And please post what you go with in the end. I would love to see the finished article.

I think going for a plain look would really enhance the classic style. I hope the images below help. Patterns will make the area too busy.