When buying a council property at a discounted price, would you need to put a deposit on the house?

For example...if the house is worth £100k and you get £25k discount...therefore requiring a mortgage for £75k. would you need to put a deposit down, or would this not be required with there being £25k equity in the property? if this is the case, would you be able to take a mortgage for upto 90% of the value, which in this case, would be £90k? thanks
Answer
Bought mine 11 years ago. the council valued it at £33k, with discount for tenancy i bought for £15k. got 100% mortgage plus a few extra grand for a new kitchennice luck.