I have a cream material suite with loose covers which say "DRY CLEAN ONLY" on them. I have washed them numerous times and as late as this weekend in a 60 degree wash with no problems. Do a 40 or 30 degree first to see how it goes. I dry them on the clothes line and iron as usual before puting them back on, I have two number three seaters and an armchair and a pouffe. They usually look a bit dodgy (small) after the wash but always fit back on ok afterwards (Thank God)
I sent the cushion covers to the local dry cleaners a few years ago and when I went to collect them they were still wet - they had washed them instead of dry cleaning them!
My mother-in-law washes her material suite regularly also.