Commuters in Kent and Sussex are being reminded they may need to make alternative arrangements if they're travelling to work over Christmas.
Upgrade work will disrupt rail services from Brighton to London and many Kent trains will not stop at London Bridge.
Rush-hour passengers on a trouble-hit commuter rail route between London and Sussex have faced more travel misery with delays and cancellations due to a signalling problem.
Three days ago, the Southern train company introduced a new timetable in an effort to improve services, particularly between London and Brighton.
But a signal problem at Haywards Heath in West Sussex led to hold-ups of up to one hour between London and the Sussex coast. A number of trains were cancelled, with passengers packing into the trains that were still running. Many passengers had to stand and Southern apologised for the overcrowding.
Among the axed services was the 7.29am Brighton to London Victoria which failed to arrive on time throughout last year.
Disgruntled travellers expressed their anger on Twitter. Leila Mekacher wrote "Southern Rail bunch of jokers! Will there ever be a day without issues?"
Lewis Cook tweeted: "Southern trains are just useless," while Steve Slack wrote: "Southern Trains. New timetable, same old service."
Thameslink and Gatwick Express services were also affected, while earlier there were delays on London Overground following a broken-down train near Willesden Junction in north-west London. Later it was revealed that the problem at Haywards Heath was a broken rail.
Some trains were terminating at Gatwick, Three Bridges and Haywards Heath, while it was hoped that buses could be laid on to replace trains. Some of those caught up in the latest disruption were also unlucky enough to be travelling from Sussex to London at the end of last month when power supply problems near Clapham Junction station in south London led to chaos.
One train, the 6.55am from Brighton which should have reached Victoria at 8.15am, was stationary for hours and was eventually towed into Streatham in south London just before 1pm.
Network Rail said: "We apologise to passengers whose journeys have been delayed this morning as a result of a track circuit defect just outside the Haywards Heath area. Trains are being cautioned through the affected area at 20mph and our engineers will be on site to rectify the problem once the morning peak is over."
Only a third of rail passengers are happy with the way their train company deals with delays or cancellations - that's according to a survey by customer watchdog, Passenger Focus. One of the most common complaints was that information on Twitter was more up-to-date than that provided by the station. The findings have ben sent to rail companies.
Passenger Focus was asked to carry out the survey by the Office of Rail Regulation, with the findings being sent to the train companies.
Passenger Focus said the tone of announcements needed to signal that the train company was "on the passengers' side" and could be as important as the content of the messages.
Other recent Passenger Focus research has shown that this can enhance passengers' trust in train companies.
ITV Meridian spoke to Chief Executive of Passenger Focus, Anthony Smith.
Rail fares on South West Trains will increase by an average of 4.1% from 2 January 2013, the company confirmed today. The cost of a single journey will rise by an average of 16p. The company says fare rises are determined largely by government policy - reflected in the Autumn Statement.