Your course start date is the date given on your CAS. If you are doing a course that is six months or longer, or for a pre-sessional course that is less than six months, you will be able to come to the UK up to one month before the start date of your course. If you are doing a course that is less than six months in length (and is not a pre-sessional), you will be able to come seven days before your course start date.
If you are studying a course of more than 6 months, your visa would normally be issued as a 30 day entry vignette (sticker) in your passport and you will need to collect a Biometric Residence Permit (BRP) after arrival in the UK. As a result of the pandemic, UKVI will issues 90 day entry vignettes to allow for more flexible travel arrangements to the UK
If you are studying a course of less than 6 months, the entry visa you received in your passport should be endorsed to cover you for the full duration of your course and you should not need to collect a BRP once you arrive in the UK.
Immigration permission granted but cannot travel
If you have obtained your visa but not yet arrived in the UK, you must check that the visa sticker (‘entry clearance vignette’) in your passport will still be valid for your intended travel dates.
You may find that the entry clearance vignette is about to expire or will have expired by the time you wish to travel to the UK. In this situation you will need to apply for a replacement sticker. There are two ways to obtain a replacement sticker (entry clearance vignette):
If you chose not to come to the UK during the time given on your 90-day vignette:
You must apply for a replacement vignette that is valid for your intended travel dates. You will need to pay £154 for this new application and provide your biometric information again. You do not need a new CAS and you will not have to pay the IHS again. If your TB certificate is more than 6 months old you will need to obtain a new one. You need to read the information on the UKVI website about how to apply.
Your application will be for a Transfer of Conditions (vignette transfer):
You should state the country that you wish to apply from when you apply online.
In the additional information section you should state that you have been granted a Student / Tier 4 visa but you need a new 90 day vignette as you have not been able to (or will not be able to) travel to the UK before the expiry date of the vignette that you have been issued