Hi Chris, I do not think the water is coming from the spray arm mount.I expect it is coming from the recirc motor hose and spraying upwards.I have never had a spray arm leak in the base ever.Look at the hose that goes from the motor at the top to the sump, you should feel a split.If so you have to replace the complete motor and this is approx £250 inc vat fitted.All the best.
FOXY
October 2008