Is our entry visa still valid ?
If you are a citizen of the United Kingdom, your visa is valid for 90 days for a total period of 180 days. So you have to count 90 days from when the visa was received to learn its exact expiry date. Your stay cannot exceed 90 days. If this period does not cover your holiday you will need to obtain another Turkish visa at the official point of entry (e.g. International airport, seaport or land border).
You can apply for an electronic visa online, before you arrive in Turkey, please click on this link to place your application and access full details: https://www.evisa.gov.tr/en/