I must admit to being surprised by the extent of the amber warning, especially the wording - I thought SW England was Devon and Cornwall, with most of the amber warning map showing up the West Country. I believe the main point of severe weather warnings though is to alert people to the risk, hence 'be prepared', rather than carry on with your day with no idea of the potential for bad weather. Who does National Rail take their day to day forecast from anyway, public warnings come from the Met Office, but there are many firms out there selling forecasts to companies?
They do not take their day to day forecast from public warnings. They receive tailored forecasts from the Met Office. The public warnings we see are based on the warnings issued to individual local authorities and other public utilities including Environment Agency, Natural Resources Wales, Highways England, Network Rail, water companies, electricity distribution companies etc. These bodies have in addition personal contacts so that they can talk directly to a forecaster familiar with their area. The Environment Agency have some control rooms with permanent Met Office staff in place to work with hydrologists to produce flood forecasts.
Unfortunately the type of rainfall we are experiencing at the moment is extremely difficult to forecast. If you read the reports of flooding you will hear often of severe flooding in one place and only drizzle in another place nearby.
The Boscastle flooding of 2004 was not forecast for this reason. Now computer technology has made it possible to forecast the likelihood better but not the location with the same accuracy - hence the blanket warning.
The warnings are used by the authorities to do what it says - be prepared - so Environment Agency and Natural Resources Wales flood management control rooms were staffed up, local authorities put staff on stand-by to deal with any consequences. All sorts of actions were going on in the background.
And there was flooding in the Orange area and local authorities and the Environment Agency took action where it occurred to deal with the consequences. There was flooding in Gloucester, Oxford, in Herefordshire and at Didcot Station. The Environment Agency monitored river levels through the night and issued flood warnings (as I write there is still one in force for the Lambourn Valley in Berkshire).
All these behind the scenes actions took place because the warnings were issued.
Contrast the 1953 coastal flooding where 300 people were killed who could have been saved by appropriate warnings (as the floods moved down the coast quite slowly from north to South), but there was no system for warning anyone else and no one was monitoring the flooding nationally to see the pattern and make a forecast.
Whether Network Rail should have put a blanket speed restriction on - I am not able to judge. But there are more to these warnings than we, the public see.