Generally loomstate means straight off the loom, no washing (can sometimes leave fabric a bit oily), no sizing, no dyeing (doesn't mean uncoloured, just not overdyed), and freqently no tidying up of loose ends or darns.
I think you might be best to give them a phone and ask just what they mean by the term, and ask if it's suitable for your needs.
I've always found them very helpful, and they'd rather have satisfied customer than one who complains about them selling the wrong stuff.
£10 is a really good price for ventile
Cheers,
Toddy