Thanks for your enquiry.
I am afraid you don't have a right to buy the Freehold- Leaseholders living in a block like yours are only legally entitled to a Lease extension of an additional 90 years at a peppercorn rent (ie zero rent), provided they have owned the Flat for 2 years.
If the Freeholder did voluntarily wish to sell the Freehold of the building, he does need to give you the right to buy it first, before selling to a third party, but this would have to purchased by all 3 of you (ie all the Leaseholders in the whole building) and it would not be possible in these circumstances for you personally to purchase only the "half of the Building in which your 2 Flats are situated.
I hope this assists and sets out the legal position.
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Hi Sonia, if I have helped, I would be grateful if you could rate my answer. Kind Regards Al