You mention that the will specifically says that the house can either be sold, or kept with each of the 8 owning one eighth.. and that the two executors can decide which option to go with.. (but you don't have a copy of the will)
Well, it could be that that clause in the will is illegal, and un-enforceable.. you'd need a solicitor or a barrister to let you know for certain.. but for example, a married man must leave half his estate to his surviving wife, .. if he doesn't do this in the will and gives the money to someone else then she can get her money somehow, possibly by applying to the High Court or something...
I'm not a solicitor so I don't know how it works.. but I wouldn't necessarily accept that just because it says something in the will that that is how it has to be.
I feel you'll need a solicitor, firstly to write to the executors and get a copy of the will, and secondly to apply to the High Court on your behalf for your one eighth share, either by selling the entire house, or selling your share, for a price you're happy with, don't take less than it's worth... I know the solicitor costs money you may not have, explain to the Solicitor that he'll get paid when you get your one eighth... also ask him if you can get your expenses refunded (by the executors personally, not by the estate) in having to chase up the executors, this refers to the issue of the executors refusing to give you a copy of the will, in spite of the fact that you are apparently entitled to it.
I hope it works out well...