Hi
You can remove the sump in car without removing the subframe. You will however need a cross strut lifting beam, as the sump doesn't quite clear the subframe with the engine sat in it's usual position, you need to lift it a couple of inches. You also need to either remove or loosen the air con pump from the block, as there's an m6 sump bolt sat behind the bracket that is impossible to get to without a turned down socket.
Did this to confirm my oil pump chain had broke. I hope you haven't had a similar fate!
cheers
Robin