Clean, old wool blanket for lining door curtain (Clive Vale TN35)

I'm looking to line a single cotton doorway curtain with something a bit more thermal to help keep the heat in my sitting room - ideally an old wool blanket would be perfect. It doesn't really matter if it's holey or very worn, just so long as it's reasonably clean. If you have something like that or similar that might work, please do get in touch. Thank you.