My mother has a BT Studio 4100 plus phone, one handset in the living room, the other in the kitchen

The one in the kitchen is fully charged, but when you pick it up either to make a call or answer one, there's just a loud buzzing noise. The other handset is fine

There's no fault showing on the display, and it's not that old

Any ideas anyone?

Thanks!

Swap the handsets around, does the kitchen still cause a buzzing with the living room handset ?

No, just the one handset - whether it's in the charger or away from it

Must be the handset then. If you take the kitchen handset into the living room where I presume the base station is (sending out the signal) and it still buzzes that is all it can be (I think).
If less than a year old it may be covered by guarantee.

Thanks - yes, I feared it might be the handset. Of course, Mum can't find the receipt . . . although she has one for everything else she's bought for the last sixty years - just not the one we want!

Oh well, will have to see if we can buy just the handset

Have a look at Ebay.

Thank you!