This 'event' wouldn't be a certain Rugby match would it? If it is, I'm not really sure we can be of any assistance.
There is another thread for the South East who'll have better local knowledge, but London area is under an Amber warning for both Saturday and Sunday.
Check the HIRLAM model animation on the previous page, which shows the South East under heavier snow early on Sunday.
Some of us were impressed with the Hirlam's handling of the snow distribution last time.
Best of luck! For the trip... not the Rugby.
Edit - Having said all that... the amber warning ends early doors on Sunday and the MO suggests the snow will have pushed through, with the heavier stuff falling later on Saturday.