Ask an Property Solicitor. Get an Answer ASAP.
Good day your question has been forwarded to me to see if I may be able to help.
Thanks for your patience. The fact that there was nothing in writing does not prevent the estate being able to take steps to remove her from the land and/or recouping money owed to your father. As, the money would now form a part of his estate. The executor through the solicitors may take steps to give the required notice for them to leave and also notify them of the intention to take steps to recover monies owed. Hope this helps. All the best.
I would not recommend that you simply stop them having access, you could run afoul of the law in doing this. Once the executors have obtained probate they may send the required notice to them to leave. if they fail to leave, then they may commence recovery of possession proceedings to recover the property.