A Separation Agreement can be legally binding, but my own view is that it would not be likely to be enforceable unless two conditions were satisfied ; firstly, there had been a full disclosure of the financial position of both parties and secondly, that both parties had access to legal advice.
A Separation Agreement does not prevent either spouse applying for financial relief afterwards, so it is not guarantee of finality but the Court can certainly take it into account. You need to remember that the Courts will not enforce an agreement which, in the Court's view, is unfair to either party.
Thanks Mike, thought we could use this agreement in the first instance and avoid unnecessary solicitor fees and see how things progress between us. Even though we are separating and will be selling the house we don't want to divorce straight away. Would you suggest using solicitors to draw this up or get a solicitor to check it?