Was caught up in this last night, coming back from the Millwall match.
Journey down (about 3ish) was fine, no sign of any disruption and certainly no warning that the flooding had come back and that the journey back could be disrupted.
Before getting on the tube at London Bridge, happened to check my phone and saw that nearly every train north from St Pancras was cancelled so absolutely legged it once at St Pancras from the Northern line platform to the TL platform, just about made it for the 22:32. Apparently after that there was nothing until 23:48?
As usual with Thameslink, things can go wrong and usually it's outside their control, but a little bit of communication really wouldn't go amiss!