I see the Guardian is still pursuing its anti-monarchy agenda, which is clearly more important to its journalists than simple things like getting the facts right.
Anyone can see draft legislation before it is passed by parliament.
Anyone can lobby the government for changes to draft legislation.
The Queen exercises Queen's consent in accordance with advice from the government.
The suggestion that the Queen has used Queen's consent to force the government to make changes to proposed legislation is simply wrong.
In relation to the specific case mentioned here, the "special exemption" referred to applies to land owned by the government, government departments, the Crown Estate (revenues from which go to the government) and the Duchies of Lancaster and Cornwall (which are held in trust for the sovereign and the Prince of Wales respectively). It is normal for all of these to be grouped together and classed as Crown land for the purposes of legislation, so the Duchies automatically received exemption - the government was never going to give the right to buy to residents of properties on government land. I very much doubt that any lobbying was required at all. I note that the Guardian does not produce any evidence for their assertion that the Queen lobbied for changes. The private estates (Sandringham, etc.) are not covered by this exemption. If they were, I would see that as evidence of a change from royal lobbying. A standard exclusion for Crown lands is not evidence. I would be very surprised if such an exemption was not included from the very first draft of the legislation.
The standard of journalism on show is typified by the three cases quoted.
Case 1 carefully omits to say that the exemption covers all land owned by the government, Crown Estates and Duchies. It is completely wrong to say that residents of the Duchy of Cornwall were barred from buying their houses if the properties were deemed to have important architectural or historic features. That completely misunderstands (and hence misrepresents) the relevant portion of the Act which applies to all landlords (not just the Duchy of Cornwall) and is about the process to be followed if they want to retain powers of management of their estate after tenants acquire the freehold of their house. There is nothing in this part of the Act that bars anyone from buying their house.
Case 2 claims that Leasehold Reform, Housing and Urban Development Act 1993 was altered to give exemptions to specific properties in the Isles of Scilly and Dartmoor. No such modification was made. Dartmoor isn't mentioned in the Act at all. The Isles of Scilly are mentioned but only to make Part 1 of the act applicable there, i.e. to give tenants in the Isles of Scilly the same rights as tenants in England (with, of course, the same exemption for Crown land).
Case 3 which claims that the Commonhold and Leasehold Reform Act 2002 was modified to include houses in Newton St Loe in Somerset. No such modification was made. There is no mention of Newton St Loe or Somerset in the act. What actually happened is that the Crown authorities agreed that, notwithstanding the exemption in the Act, they would agree to allow residents to buy their properties or extend long leases unless the land is held inalienably (which means the Crown cannot sell it), there are particular security considerations, where properties are in or intimately connected with Royal Parks and Palaces, or where there is a long historic or particular association with the Crown. Newton St Loe, parts of Dartmoor and some other areas fall under this final definition. So, the Act was not altered to extend the exemption to these areas. The Act was not altered at all. Instead, the Crown agreed that it would not make use of the exemption in most areas, but the areas mentioned by the Guardian are amongst those where they would continue to take advantage of the exemption.
The journalists behind this article would have done well to consult a lawyer before writing such an ill-informed piece.