If your father left a will and this is what happened under the terms of the will, that everything went to your stepmother, it is very difficult to contest that when everything is been left of a spouse in a will but notwithstanding, you are out of time to bring a Inheritance Claim in any event.
If he died without a will:
The cut-off date for someone who dies without a will (intestate) historically here is 1 February 2009 because that is when the exemption rate changed..
If your father died before 1 February 2009 then his spouse inherits the first £125,000 and a life interest in half of the remainder of the estate, the children get the other half of the estate.
After 1 February 2009, the limit was increased to £250,000.
Here is an article giving the date of the increase: https://www.taxpenny.co.uk/news/2008/10/intestacy-rules/
From 1 October 2014 the rules changed yet again but that doesn’t apply if your father died in 2012.
If the total value of your late father’s estate at the date of death in 2012 was more than £250,000 then his spouse gets the £250,000 plus a life interest in half of the remainder and children get the other half of the remainder on death and the half of which she has a life interest, when she eventually dies. (Yes it is complicated).
What you need to establish here is what the total value of your late father’s estate was at the date of death. If it was £250,000 or less, then the whole estate would have gone to his spouse, your stepmother. The value now is not relevant.
I did use this House Price Index calculator (which is quite useful) http://www.nationwide.co.uk/about/house-price-index/house-price-calculator#tab:HousePricecalculator
and just basing the calculations on a house on its own, if it was worth £250,000 in 2012, depending on where it is in the country, it’s likely to be worth more than £300,000 now which means there is unlikely to have been any prejudice to your financial position. There are some exceptions to the house price index increase, Wales being one of them, where the valuation will have increased but isn’t likely to be more than £300,000.
Can I clarify anything else for you?
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