Are the white flowers isolated on one or more branches, but with no pink flowers present at all on their particular branch? If so, cut out the all white branches. It's just a bit of DNA alteration, or reversion to previous genetic coding.

Thanks Bamboo... Just had a quick look and it seems from the main branches there are smaller branches and they are either white or pink blossom not mixed although they have come from the same main branch. If I cut out the white would they not grow back ? Also is it doing the tree any harm?

It's not doing the tree any harm, but you MAY find the white branches increase in number or grow faster/longer. If you do prune them out, take them back to their point of origin. You may find more grow next year, or not.

Big thanks Bamboo really helpful :-)