The standard delivery time for a letter sent from Gibraltar to the UK is 3-5 working days. This may vary depending on the time of year and the postal service used. For example, during the Christmas period, delivery times may be longer due to increased mail volume. Additionally, if you are sending a letter to a rural area in the UK, it may take longer for the letter to be delivered.
If you need to send a letter urgently, you can use a faster postal service such as Royal Mail Special Delivery or DHL Express. These services typically deliver letters within 1-2 working days, but they are more expensive than standard delivery.
You can also track your letter online using the tracking number provided by the postal service. This will allow you to see where your letter is in the delivery process and when it is expected to arrive.