If you wish to attend on behalf of a client, you will need to have rights of audience that allow you to represent clients. That involves - in the Crown Court - having a practising certificate with higher rights of audience (as a solicitor) with the Solicitors Regulation Authority or a practising certificate as a barrister with the Bar Standards Board.
If you are a lawyer in Pakistan you will not automatically have rights of audience in England.
If you wish to represent yourself as a party in proceedings, then that is permitted regardless of qualifications.
If you wish to help a family member or friend who is a party, that may be permitted but would require permission of the Judge.
If you wish simply to visit and watch proceedings, the courts are open to the public and you may come and go as you please during breaks in cases.