I had committed adultery sin (zeena) and I am not married. Now I am seeking forgiveness from Allah by not having sex again. But some times when I am so horny I masturbate by using porn movies. And putting in consideration that I am living in England.I heard that masturbation is halal, but I am not sure about masturbation using porn movies.

Honorable brother,
In Islamic law, it is prohibited to watch pornographic movies. There is a difference between mitigating one's sexual urge and arousing it in the first place. According to the opinion of some scholars, it is permissible to masturbate to mitigate one's sexual urge if it is involuntary aroused and there is a fear to commit fornication [zina]. However, practicing masturbation in the first place to arouse one's sexual urge without a necessity is prohibited in Islamic law. It is only permissible to masturbate to avoid committing any sin which may bring either physical or religious harm.
The most important means to avoid masturbation is hastening to seek marriage as soon as possible while maintaining simplicity and avoiding excessiveness and complications.
- Moderation in food and drink which contribute to stimulating sexual desire. In this regard, the Prophet (peace and blessings be upon him) recommended fasting as per his words, "O young men, whoever from among you can afford it, let him get married, for verily it is a means to lowering one's gaze and protecting one's chastity. And whoever cannot, let him fast, for it will be a shield for him.”
- Refraining from anything that arouses sexual desire such as listening to immoral songs and watching lewd images which are available in abundance in movies.
- Directing one's aesthetic faculties to permissible channels such as painting flowers and nature scenery which do not arouse sexual lust.
- Choosing righteous pious companions.
- Occupying oneself with worship in general.
- Avoiding submitting oneself to sexual thoughts and instead merging in the community by engaging in activities that distract oneself from thinking about sex.