The law says you are entitled to at least 1 week's notice after one month and up to 2 years' service. After that you are entitled to 1 week for every year of service up to 12 years' service. So for 6 years' service you would be entitled to 6 weeks' notice and for 20 years' service you would be entitled to 12 weeks' notice.
These are minimum periods and a contract of employment may give a longer entitlement.
In cases of redundancy, notification in advance of the formal notice of termination of employment should be given in order to see whether an alternative to redundancy is possible. In cases of dismissal for serious misconduct the employer may decide not to give notice, e.g. carry out a summary dismissal, although it would still be necessary to act fairly and reasonably, and within the statutory grievance and disciplinary procedures.
Just One More Click: Doggy drama about staying safe online at work.