List of British extinct mammals by Wikipedia

Arctic lemming: 8000 BC

Aurochs: 1000 BC

Coypu: 1978 (nonnative)

Moose: 1500 BC

Eurasian beaver: 1526

Eurasian brown bear: 1100 AD

Eurasian lynx: 700 AD

Grey whale: 598 BC

Gray wolf: 1743 (Britain), 1786 (Ireland)

Irish elk: 6000 BC

Narrow-headed vole: 8000 BC

Pika: 8000 BC

Root vole: 1500 BC

Saiga antelope: 10,000 BC

Steppe lemming: 8000 BC

Tarpan: 7000 BC

Walrus: 1000 BC

Wisent: 3000 BC

Wolverine: 6000 BC

Woolly mammoth: 10,000 BC

Woolly rhinoceros: 10,000 BC

Cave lion: 10,000 BC