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Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
May I ask why you are not selling the property?
That makes perfect sense.
As a joint owner you are entitled to tell the lodger that he will no longer be welcome after the set date.
Once the date has passed he will only be able to stay in the property whilst your ex is there as his guest.
When your ex leaves then the lodger will have no right to be there and you can ask him to go out.
If he refuses to leave then you can call the police to force the issue
Of course when your ex returns then his guest can return - but of course you can move things round so that he no longer has the room he has now.
I appreciate that this is not the perfect option but it is the only one available to you unless you wish to force the immediate sale of the property
Please ask if you need further details