Glad you decided to post (as this forum will help you get some support and info), but of course sorry you had to post.
OK this is what I would do.
(1) You say that endocrine therapies have failed. Do you know why they have failed? The fact is that cancer frequently changes it's receptor status (in 32.4% of cases), and it could be that your cancer has changed from being ER+ to something else such as Her2+ (that occurs in around 15% of cases and actually happened to me). If you have become Her2 + then you would require Herceptin or Lapatanib (chemo wouldn't be adequate). Consequently, I would ask your Onc to perform a biopsy (obviously that will depend on whether there is a met they can access). Don't allow your Onc to fob you off by saying cancer rarely changes it's receptor, I can provide a link to research evidence if you send me a pm.
(2) With regard to whether Cyberknife stereotactic radiotherapy would be an option for your liver mets. You obviously need to speak to a Cyberknife specialist, but in general, Cyberknife could be an option providing you do not have more than three mets, and they are no bigger than 3.5cm. If you have more mets, or they are bigger, you could look into TomoTherapy. Tomotherapy is actually an IMRT machine, but can be adapted to be used stereotactically. If you are an NHS patient you will need to be referred to either the Royal Marsden in London (not Sutton), or the Mount Vernon Hospital in Middx, or Barts Hospital in East London. If doctors there think it's appropriate, you may still have a problem because few PCT's/GP Commissioners fund it (in fact only 29 out of 150 will fund it). Consequently you may need to get charitable funding, and I believe the Marsden have a Charity that sometimes helps, or else you could approach the Victoria Medical Foundation (who paid for my Cyberknife treatment). If you want to be referred for TomoTherapy, Addenbrooks is probably the place to go.
Hope this info is of use, and let us all know how the meeting went.