If you want genuine retro bedlinen rather than the vaguely retro inspired offering from the mainstream stores, then vintage is the only answer (assuming you aren’t put off by its second-hand nature).
Taking the hassle out of trawling charity shops, H is for Home currently has a small selection of vintage bedspreads. Dating from the 1960s and 1970s, they feature floral and op-art patterns in colours that are typical of that time. Prices range from £22 to £40.
View the full range at H is for Home.