Thanks for your reply and apologies for me misreading the pint concerning your neighbours wall.
1. As the neighbour's wall is classed as a Party Wall for the provisions of the Party Wall Act, The Act says that the party intending on demolishing any such wall must first of all serve Notice on the adjoining owner and must not cause unnecessary inconvenience to the adjoining owner (you).
The party carrying out the works must provide temporary protection for adjacent buildings and property where necessary. Hence, the developer would be under a duty to serve Notice on you before any work is carried out by them, and it is then for your Surveyor to liaise with their Surveyor to agree a satisfactory schedule of works (called a "Party Wall Award"), to include the erection of temporary fencing after the demolition has taken place.
2. The Party Wall Award will also set out the terms on which the developer is entitled to gain access to your property, if so required.
Without such an Award being agreed, the developer does not have any legal rights to enter your property without your consent UNLESS there are such rights granted in his title Deeds. It would not be commonplace for these rights to exist, but you would need to get a local Solicitor to check this point for you.
Under the Access to Neighbouring Land Act, which in itself is a lengthy Court process, the developer does not have any legal rights to obtain any such Order from the Court, as this Act only covers necessary repairs to an existing property and does not cover rebuilding a property for development reasons.
3/4 As mentioned above, the Party Wall Award will deal with both these issues and you would have a say in the replacement boundary and I have already mentioned the security issue above.
I hope this assists you and sets out the legal position on this scenario.