A spouse or dependant visa is not automatically cancelled when a couple separates, begins divorce proceedings or stops living together. The permission remains valid until its stated expiry or until the Home Office makes a cancellation decision. The relationship requirement on which the permission was granted may nevertheless have ceased to be met.
The official position is that the Home Office must usually be told where limited permission is based on the relationship, whether the person affected is a spouse or partner under Appendix FM or a dependant on a work or study route. The immigration question should be addressed when the relationship has permanently broken down, not deferred until a final order of divorce is made.
Notification and route strategy are distinct decisions. Telling the Home Office does not make a new application. Equally, an application under a different route does not remove the need to give an accurate account of the relationship history. The safest course is to settle the factual date, present permission, family position and next legal basis as one controlled chronology.