I know linen is not your first choice but Primark currently have their linen trousers at only �8 a pair in black, white, khaki, sandy colour. I've washed them myself and after line drying you can get away with not ironing them.
They are quite a long leg length though (I'm 5 foot 5) so I just rolled mine up.
I seen some in H& M the orther day they were much thicker than the linen however im nt sure they were cotton either......also try dorothy perkins they have a great petite range