If you really do mean a pole (as distinct from a curved rail, where the runners attached to the curtain slide along the front face and are hooked around the front face) then I fear what you are asking for is a mechanical engineering impossibility because the forces are too great. Curtains are heavy.
A curved pole is of course possible, but it has to be supported regularly by brackets attached horizontally into the wall above the bay, otherwise a massive downwards force from the weight of the curtain pulls the curved pole downwards when the curtain is closed and the whole structure twists.
So the simple mechanics of this suggests a closed curtain ring (around the pole) cannot be pushed past any horizontal bracket mounted to hold up the pole.
Therefore you cannot have a curtain whose poles can be slid past any mounting bracket - the curtains have to be located between the brackets, and the curtains are closed up between pairs of brackets.
That is not true of curved rails, but they have other problems (the curvature makes it harder to pull the hooks along.
You could try talking to either John Lewis or Laura Ashley to see their solutions to this.