Uk - Have our rental home valued without landlord consent?

We currently rent a house and would really like to buy it. We contacted the landlords and they said they were going to sell it at the end of our tenancy in February 2016. We said that we would be interested in buying but could not afford to until August 2016. This conversation happened a month ago.

I have been really looking into it since and looking at mortgages and savings etc, and I think we might be able to buy it now if we got it for a good price. I would like to have a valuation to confirm the price and weather we could realistically make an offer just now. I Don't want to go to the landlord for him to agree a valuation, then for me to say we can't afford it now let's just wait until next year like I originally said. I feel like I would be messing him around, especially as he lives in another country!

I have looked at sold prices in the nearby areas but all of those houses have been done up and presented to a high standard. The house we are in needs a full renovation. New kitchen, bathroom, carpets, decorated. There is Woodchip on the walls and an old 50's hideous fireplacE. It's a real doer upper and I reckon the renovation would cost 40-50k for a basic renovation. There is a dodgy conservatory that leaks and an outdoor toilet that we would need to get rid of too. So I find it hard to estimate the value when the other houses in the street do not have this work needing done. How much discount would be get essentially?

Any help would be very much appreciated.

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