How long is the British visa valid?

British tourist visa is valid for 2 years, multiple entry, and the stay time is 180 days.

You can postpone the trip, but if you want to change the appointment time after the appointment, you need to make an appointment 24 hours in advance.

You don't have to follow the submitted itinerary. The travel itinerary is just to help get the visa materials, as long as you promise to enter and leave the country within the validity period of the visa.

Data expansion:

Applicants who want to change the appointment time after making an appointment need to make an appointment 24 hours in advance. If the submission time is less than 24 hours, the applicant will not be able to change the appointment time. After changing the visa appointment time, they can make an appointment according to the system prompt. Applicants do not need to print after changing the appointment time, but it is recommended to take photos or save them in their mobile phones for emergencies. Applicants do not need to pay any visa fees after rescheduling their application for a British visa.

Generally speaking, a British visa is valid for two years. If the applicant intends to go to Britain within two years, he can also apply for a British visa according to the previous appointment time. If he doesn't have time to apply for a visa, he can also cancel his reservation in official website. However, the applicant needs to cancel the appointment two days before the deadline. After the cancellation, the British Embassy will help the applicant to refund the fee, but there will also be cases where the refund fails.

References:

Goc. uk- Apply for a UK visa to China.