Thanks for your reply.
From a Stamp Duty (SDLT) point of view, this is calculated on the Purchase price- so, if you were only to pay say £250,000 then SDLT of £2,500 would be payable. If the Price you pay is over £250,000 then SDLT is payable at a rate of 3% of that price.
So, the lower the consideration, the lower the SDLT is, as SDLT is not payable on the market value of the property- it is payable on the amount you pay.
From your step father's tax point of view, Capital Gains Tax (CGT) may be payable upon any Sale to you. Unlike SDLT, CGT is calculated on the market value of the property at the date of the Sale, rather than the price the property is actually sold for.
CGT is payable on any property you own which is not your principal place of residence,if any increase in value of the property has taken place from the date he acquired the property and the date he sells it or gifts it.
I hope this sets out the legal position, but please let me know if you require further clarification.
If not, I would be grateful if you could leave positive feedback.