Refused fertility treatment because partner already has children

Hi, i just wondered if anyone had any advice or has been in my situation.  My partner and I have been ttc for a little over 18 months now obviously with no success.  We have gone to see our GP and have both been given preliminary tests, I had an ultrasound which was all fine and a blood test which showed I am ovulating and my partner has had a SA test which was also fine.  We have now been told that because he has children from his previous marriage, that we aren't seen as a "childless couple" and therefore aren't entitled to any further investigation/fertility treatment under the NHS.  If we want to go any further we have to fund it ourselves, which our GP said could cost anything up to £15k depending on what is wrong, what medication we need etc.  We were absolutely devestated when we found this out and couldn't believe that this could be true.  His children are both teenagers.  We hardly ever see them because their mother is very difficult and moved them very far away.  Plus, as much as I love them, they aren't my children!! I'm a 29 year old woman and of course I want my own children. I just can't explain how upset and frustrated I am by all of this, which then doesn't help with the ttc!! I'm so angry that kids can have kids and peole who can't support kids can have kids and nobody tells them "you're not entitled to children", that would be against their human rights, but because we need help with it we are told we aren't entitled to have children even though we work hard to be able to support a family, own our own home and have waited until the time is right for us to do it.  Has anyone else been in this situation?  Does anyone know if there is anything we can do to appeal this?  I just don't know what to do, £15k for private treatment it just completely out of our reach. Thanks x