We put an offer in on a house in Oct, after what I believe

We put an offer in on a house in Oct, after what I believe has been a conveyancing mess, our mortgage was about to expire and we secured an extension for another month. On Thurs we met with our solicitor who instructed us we could complete on Fri 13th on the last day of our mortgage offer and that everything was in order. She then emailed at 6.01pm Friday with this statement :
JA: Where are you? It matters because laws vary by location.
Customer: Not make any changes without consent of the Landlord or Ground Rent Collector. As advised, there has been a structural alteration on the property. The position is that the Lease to your property contains a clause which states that if any structural alterations are to be carried out to the property then consent must be obtained by the Landlord/Freeholder/Ground Rent Collector. The seller’s solicitors reverted and stated that the extension was done prior to the seller’s ownership and as such they do not have such consent. When the seller’s bought the property their solicitor should have picked up on this issue and resolved it then but it seems to have been bypassed. Usually in these situations, indemnity insurance is suggested as a form of protection so that if in the future you are approached by the Ground Rent collector regarding this extension and you are penalised you can claim on the insurance, however we do not believe in this caseyou will be sufficiently protected as there is no guarantee that the Ground Rent collector is not already aware of this alteration and this will invalidate your policy. We strongly advise you not to proceed without the consent as you are putting yourselves at risk of being penalised heavy in the future. This may incentivise the seller’s to apply for the consent however please do note it may also make the transaction fall through as the seller’s could decide to withdraw from the transaction. If you do decide that you wish to proceed with the transaction without the retrospective consent in place then this will be at your own risk and we will require confirmation that you are proceeding with the transaction against our advice.
Again, you will note that these clauses t
JA: What steps have you taken so far?
Customer: Bolton, England
JA: Is there anything else the Lawyer should know before I connect you? Rest assured that they'll be able to help you.
Customer: we have taken no steps as unsure what our options are, is there a possibility to resolve this before Fri so the sale can go ahead