Which DVLA address?
At one time, there were a whole range of addresses around the UK for the DVLA as they had regional offices. But these all shut down in 2013 and now they operate from a single location in Swansea. The main address can be used for everything from sending a V5C when you change your car to returning a license to change your name.
The main address is DVLA, Swansea, SA99 1AR. The main telephone number for them is 0300 790 6802 which is open from 8 am until 7 pm weekdays and from 8 am until 2 pm Saturdays. You can also use their email service for some changes which you can access here https://live.email-dvla.service.gov.uk/w2c/en_gb/decisions/Vehicle%20Enquiries