The battery charge LED on the instrument panel has stopped coming on, on a 54 plate vRS. Can' find information in Haynes manual. Does anybody know if it is connected directly to the alternator, or does the signal from the alternator go to an ECU?

The charging warning light is supplied on one side with battery voltage via the ignition switch, the other side earths through the alternator when it is stopped so the light comes on. When the alternator turns, the earth changes to alternator output voltage (14v ish) so the light goes out as you have an equal voltage on both sides.

If yours isn't coming on at all, it could be that the light has failed, or battery voltage isn't reaching the light, or it isn't earthing through the alternator. First thing to check is your alternator output voltage, (with as much drain on the electrical system as possible), should be at least 14v at high ish revs. That's probably the easiest check, if it's not right then you may need a new alternator. The other two will need more work to track down, obviously the light is easiest to check first, lack of battery voltage could take longer to sort.

Alternator sense wire will be broken at the connection on the front of the gearbox. Very common, and covered on here dozens of times.