Hi does anyone know if the 2018 RRS side vents can be fitted to previous models? Have a 2017 model but quite like the new vents although they look a little wider so not sure if they will fit.

No, they don’t fit as the wings are different and the shape/size of the new „fake“ vents are now different.
Check yourself pictures, pre facelift vent starts direct under the hood and the new ones are not touching the hood.

(Pre—Facelift very good visible in my avatar

Best
René 2012 RRS HSE SDV6, BOURNVILLE 12/12-10/14
2015 RRS DYNAMIC HYBRID, CAUSEWAY GREY 1/15-7/18
2018 RRS DYNAMIC P400e, BRITISH RACING GREEN 8/18-8/19
2019 RRS DYNAMIC P525, SILICON SILVER 8/19-