Yes, if you are not offered a place at your top-choice primary school in the UK, you can join a waiting list. The waiting list is maintained by the local authority responsible for admissions in your area, and it is used to allocate any places that become available at the school.
When you receive notification of the school your child has been offered a place at, you will also be informed if you have the option to join a waiting list for any of the schools you listed on your application. If you choose to join the waiting list, you will be placed in order according to the school's admission criteria, and you will be notified if a place becomes available.
It's important to note that being on a waiting list does not guarantee that a place will become available, and it's recommended that you accept the offer of a place at another school while you wait for a place at your preferred school. If a place becomes available at your top-choice school, you can then choose to withdraw your child from the school they have been offered a place at and accept the place at your preferred school.
Waiting lists are usually maintained until the end of the autumn term, after which they are disbanded. If you still wish to join a waiting list after the autumn term, you will need to contact the local authority to find out if this is possible.