So you have your train at St Ives, & you're going to leave it overnight to charge. Therefore time, & who does the plugging/unplugging isn't an issue.
You fit either;
OLE (needs all the usual physical equipment, & has an exposed high voltage wire, & someone has to raise the pantograph)
3rd rail (you could control it so it's only live whilst charging, but you've still got an exposed contact, & someone has to lower the collector)
charging cable (can be locked to the socket on the train, so no exposed contacts, & also includes a communications protocol, so that battery state & 'smart' charging* can be managed)
*smart charging means that the battery state is assessed, & then the correct amount of power is supplied to charge the batteries in the most efficient & least damaging way.
You don't just dump power into a battery until it's full, doing so shortens it's life.
Those methods of getting electricity into trains is for running live systems, battery charging is different.