According to this all trains through Worcester Park are currently cancelled:
Description.Electrical supply problems are causing disruption at Worcester Park.
Because of this, there are delays of up to 40 minutes between Epsom and Wimbledon. These delays are expected to last until approximately 15:00.
15.00?? Hmmm... I'd say that with the trains out of position they'll be a knock-on effect and that it's going to be an evening of pain on the trains. Keep an eye on the live departure board for Worcester Park here or London Waterloo here. It seems to be having an effect on other lines too so I'm not sure going to New Malden would help much.
Ah well. Have a great Christmas and New Year!