The UK is on the list...
The following countries have railway companies that accept the Interrail Pass EURO 2024: Austria, Belgium, Bosnia & Herzegovina, Bulgaria, Croatia, Czechia, Denmark, Estonia, Finland, France, Germany, Great Britain, Greece, Hungary, Italy, Latvia, Lithuania, Luxembourg, Montenegro, Netherlands, North Macedonia, Norway, Poland, Portugal, Republic of Ireland, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, TΓΌrkiye
Residents or citizens of the following countries can also buy an Interrail Pass EURO 2024: Albania, Andorra, Belarus, Faroe Islands, Gibraltar, Iceland, Kosovo, Liechtenstein, Moldova, Monaco, Russia, San Marino, Ukraine, United Kingdom, Vatican City