I doubt that it can be said about Britain to have been "the morally highest out of the colonizers".

The most obvious difference between Britain and the other colonizers is that in most British colonies the former native populations have vanished in a much greater proportion than in the colonies of other countries (with the notable exception of India, which was much more populous since the beginning and where much less British have immigrated).

Based on this difference, Britain does not seem to have been the morally highest, but the opposite.

The current higher solidarity between some former British colonies is based exactly on the fact that these are the colonies where the natives have been almost completely replaced by immigrants, which are more closely related between themselves due to their common origin.