Yes. To attend a car track day you'll need a full UK driving licence or an international equivalent for the vehicle you'll be driving.
If you'll be using a non-GB licence, please make sure the photocard clearly shows that the licence holder is able to drive the class of vehicle in question.
To check that your international licence allows you to drive in the UK, please check using the Government website.
Alternatively, competition licences can be used in place of a standard road licence, with National B or higher MSA/FIA race licences accepted.