Unfortunately, you can not drive a hire car in the UK if you are 19 years old. In most cases you need to be at least 25 but you can still rent a car if you are over 21. Always check the terms and conditions for each supplier and their age requirements.
Because this is the case, you will need to wait until you are the correct age to hire a car. As each supplier is different, always check back to see if changes have been made.
Read more about age restrictions here.