Thought I ought to start a new thread. I know the situation in the west of Wales is pretty dire ( massive understatement) but a bit of a situation could develop in the se tomorrow. Not to the same level, the geography is rather different but nevertheless.
Models are differing hugely, so there is a lot of uncertainty. However the nae, which looks at mid sized features has perhaps 50-100mm showing. showing here a 6 hour total of 50 mm around the Sussex area.
Gfs, a coarser model shows less rain but moving further north.
I guess the only advice I can give is to keep an eye on the environment agency's flood page if you live in a flood prone area And the met office warnings page