Remington hair clippers only works plugged in (Westbury Fields BS9)

Remington hair clippers, HC365. Been well used and the battery no longer charges but it still works fine plugged into the socket. Smooth cutting blade and easy to use. Has guide combs of 25mm, 18mm, 12mm, 9mm, 7mm and 3mm. With a right and left taper one for around the ears. Comes in a handy plastic case with a couple of black combs which have never been used. Plus some hairclips which have been used once or twice. Been cleaned regularly after each use but has been sitting around unused for a while and is a little dusty.