Unfortunately where a folio is subdivided and mapping is involved it could well take up to 2 years for registration to complete.
However if the assents and applications ( the affadavits you mention, I assume) are signed by the per rep and the grant has been extracted then you are already the 'legal' owners and the beneficial owners, just not the registered owners.
Thus, armed with copies of the documents and a dealing number from the land registry, you could do pretty much anything with the land that you want to, including mortgaging, transferring, subdividing again or selling.