A level Physics diffraction confusion

If different wavelengths of light are diffracted by different amounts/at different angles then how come when a white light is shone through single/double slits or a diffraction grating, the bright fringes apart from the central one are rainbow - I mean I do understand the theory behind this - but I don’t get why there isn’t a fringe of only red, a fringe of only violet etc - because shouldn’t all the light of the same wavelength be diffracted at the same angle?

You've touched on the answer but I think the picture in your mind is slightly unclear. What happens if you shine monochromatic light though a grating? Do you expect just a single diffraction? No! You have constructive interference at integer wavelength spacing. The same is true here.

Shine white light through a grating and you see the rainbow pattern occurring at integer wavelength spacings. The central fringe is still white since it is not diffracted. The first rainbows (m= +/-1) show the diffracted pattern - each colour appears at a slightly different place as the wavelength of the light is different (eg: green and red light have different wavelength). This pattern then continues for m = +/- 2, you see two more rainbows where the light has been diffracted.

"I don’t get why there isn’t a fringe of only red, a fringe of only violet etc - because shouldn’t all the light of the same wavelength be diffracted at the same angle?"
There is - but within each rainbow! But white light contains all the colours hence you see a rainbow. I think you have forgotten the condition for constructive interference so perhaps read over that for peace of mind.

Ahhh that makes sense yep thanks I wasn’t thinking about the path difference and interference properly - so it’s like a rainbow because all the different wavelengths have their own sort of interference pattern?