No reason why not, usual negotiations apply. It rather depends how much they want to sell 2 pieces. I made an offer on a Lucy Young piece at a gallery in Cardiff and after a little give and take a deal was done. We aren't talking thousands either. It's easy for them to spout pretentious gallery speak but it's still sales! I'd stick to your guns.
Eta after a quick Google I suspect we are talking about the same group so they do deal