Not only does the battery light come on when start the car it stays on ,and increases in brightness the more throttle you give,and now stays on when engine is off and the key is out of the ignition,whats going on ?

check connections on back of alternator,,

all looks good cant see nothing loose,when i turn key to position 2 for the heater plugs it goes out,when i fire it up straight back on

What condition is your alternator in ? Have you been in any water ? I've just had to replace mine as the bearing went the light come on the a mile up the road I had to pull over as I could see smoke. When I opened the bonnet my alternator was glowing bright red, I was stood in a pub carpark peeing on it to cool it down(should have turned spots off really lol)

If its getting brighter when you put you revs up then I'd say your alternator isn't projucing enough power and even though its making more power when you rev it, it's still not enough to run everything else, find some where to get it reconditioned as its cheaper don't wait till the bearings go as it destroys the case too and it can't be fixed

If the light stays on with the key out the ignition then the diode pack is shot.
Simple as that.
It has nothing to do with the bearings.

the rectifier is knackered in the alternator.you will probably find that the alternator will get red hot when its running. it can be repaired but can be a pain in the arse so would be just as easy to get either a recon or used unit.