I tried everything on my tubes such as Fairy Power Spray, TFR, Acetone and couldn't get the tubes clean. The tubes on my boat were severely faded and I couldn't get hold of the spandex stuff so I eventually tried PVC solvent cleaner.
I tested on a small area during the week and there didn't appear to be any side effects and then I proceeded to use on the bow area. Then to remove the mildew I then used a Dettol cleaner (a bleach) which was effective but didn't get rid of all of it.
Thought I would share with everyone the before and after pics.
Hopefully they will be no long term side effects