You should report the harassment to the Police.
They will warn your ex to stay away. If the ex does not then the ex can be arrested and prosecuted for harassment.
If your ex is illegal in the Uk then he could also be deported.
The Protection of Harassment Act 1997 states:
Prohibition of harassment.
(1)A person must not pursue a course of conduct—
(a)which amounts to harassment of another, and
(b)which he knows or ought to know amounts to harassment of the other.
[F1(1A)A person must not pursue a course of conduct —
(a)which involves harassment of two or more persons, and
(b)which he knows or ought to know involves harassment of those persons, and
(c)by which he intends to persuade any person (whether or not one of those mentioned above)—
(i)not to do something that he is entitled or required to do, or
(ii)to do something that he is not under any obligation to do.]
So report it to the Police. This will stop the unwanted contact.
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