Definitely not going to attempt this.
Here's an example from yesterday of the state of the train service to London from Kent and back again during August;
Bought tickets to London Victoria online, then travelled to local station.
9:30 in the a.m. No trains to Victoria due to incident on route, none to Charing Cross for London Bridge works. Both destination tickets now valid on high speed service to St Pancras and Tube to original destination due to this disruption. This makes us over an hour late to get to where we wanted to go, not helped by many Tube lines having restricted service or fully closed.
5:30 in the p.m. Return journey was worse; No trains from Charing Cross, still no service from Victoria, so had to travel to St Pancras, to then be told by station staff at ticker gates that our tickets were not valid. Complained to their customer services desk, who eventually let us travel.