1. Here, the "advice" would have been that this neighbour was in breach of the terms of his parole licence and he would be sent back to jail if he continues with his harassment of you. Essentially, the police are telling this neighbour that there will be serious consequences if he continue with his behaviour. In practical terms, there is little difference between being "advised" and being "Warned". However, a warning is normally given to first time offenders who are at the lower end of the scale. Being "advised" is simply being told that jail awaits any further repetition of this harassment. I would not put too much store on the words used. Essentially, this neighbour has run out of warnings.
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3. It certainly is most unusual that no complaints have been logged or that the police attendance at the property on two occasions has not been recorded. For this reason, I would suggest you speak to your local MP. As the police route has failed you, I would suggest you seek a political remedy. It is always impossible to say for definite if someone is receiving police protection. However, political will can ensure something is done about the harassment.
4. For this reason, I would suggest you speak with your local MP. This will ensure that the police take other considerations into account, apart from seeking to protect this former inmate.