Hallo Localgirl and welcome to Wikivorce the site none of us wanted to find but which is very helpful and supportive
I will attempt to give some answers here. I understand that you feel hurt and betrayed by your husband and want him to face up to what he has done - but he may never do so and you need to rebuild your life without expecting that.
Your questions
1. how to separate without too much cost
The thing that costs is parties arguing about things. If you and your husband can agree on how to divide your stuff etc it will be much cheaper. Once you get solicitors involved the bills mount up.
2. how i can reasonably get him out of the house
You can't. It is his home too. There is such a thing as an occupancy order I think, but I don't think its easy to obtain.
3. Will i still be entitled to some of his fathers estate as i am still named in his will.
If your father in law is still alive he may change his will. If he isn't what he bequeathed to you will stand.
4. What maintenence can i expect as he can and does earn a lot more money than i ever could. My income is fixed and not a lot.
Hard to say without information about his income, your income and both your outgoings. I assume that the likelihood of you working in the future is negligible.
5. I am not wanting a divorce at the moment but may consider it later.
That isn't a question. But if you want spousal maintenance from your husband you may need to divorce to obtain it.
6. My husband has not made any pension arrangements for when he retires, relying on state pension. Where do i stand on that.
If he has no pension you cannot claim it. However, his contributions to the state pension can be used to boost your own state pension.
www.pensionsadvisoryservice.org.uk/women...basic_state_pension/
has more details.