stewyb
I think you must have missed the edit that I added to my post two days ago. As you probably know Crossrail work means there are no trains at weekends at present on the Liverpool Street line and GA normally run a bus replacement service. Owing to the weather conditions even that service had been withdrawn that morning so KLM didn't want their pax arriving somewhere with no public transport connection to London. It doesn't seem to have been the lack of chartered coaches to take the pax back to LCY. SOU, on the other hand, probably had a rail service of sort sort running to London that day.
On the same subject the lack of weekend trains must be a drag on the attractiveness of SEN due to these seemingly never ending engineering works. SEN seem to have got so fed up with it that they are now running their own weekend buses between SEN and Thorpe Bay station on the C2C line and advising their pax to use this service instead of the GA line.