KEF SubWoofer, needs attention (Headington OX3)

KEF Model 20B Series 2, 70W Active SubWoofer.
In good condition for age but one channel stopped working a while back... not sure what the problem is and haven't got time to investigate - and probably wouldn't know how to fix it anyway!
Includes power lead & plug and photocopy of the manual.
10" Front-facing driver. Size: 326 x 302 x 299mm. Weight: 9.3Kg.