Help me - bath mat has stained the bath really badly

[kirstygem]

Am helping a friend clean her house before she moves outand have just discovered that her bath mat has left large yellow stain on the whitebath. Is there anything I can do to remove or improve this? She is really worried she will lose her deposit now

[Cadbury]

cillit bang gets mine clean. - if it is mould based then it might help. General scrubbing is needed too.