Stays are quite low, with the bosom much exposed
In honour of London Fashion Week - yes it is: I'm a journalist so I know these things (unfortunately) -- I thought I'd repeat the fashion advice of Ladies Magazine for June 1775:
The head-dress was ushered in at the beginning of the spring with a Small tuft of feathers which was Soon changed to two or three distinct ones of the largest size placed remarkably flat with a rose of ribbons on the fore part, and a knot Suspending at the back of the head.
The hair low before, yet rising on the forehead nearly perpendicular, in a round small toupee. The sides down to the ears combed smooth, very far back and broad behind. The corners raised but a little above the front, with two, three or four large curls down the sides, the bottom curl in many nearly upright. The bag not so low as the chin, small and smooth at bottom, in general. The robings straight, in many puckered. Stays quite low before, and the bosom much exposed. Breast-knot small ; bouquet large. The round cuff, variously trimmed, in some up the arms, was indiscriminately worn on sacques, or the loose gown, which was thrown carelessly behind, and gathered up the sides, or close to the back of the waist ; in either tied up with ribbons of a different colour.
Hats little worn ; white roses were generally worn in the shoes or slippers."
(A sacque, the dictionary tells me, is a short, loose-fitting outer garment, something like a shawl I gather.)
This from my newest Ebay antiquarian, English Women in Life and Letters, by M. Phillips and W.S. Tomkinson, OUP, 1927, p. 122. (It is not like the books the press put out now, being profusely illustrated and distinctly frivolous.)