From the Guardian:

But Peter Davies, the director of the Child Exploitation and Online Protection centre (Ceop), which carried out the research, warned against jumping to conclusions on the ethnicity of offenders because the data gathered by his investigators was incomplete, not nationwide and of poor quality.

"I would send a note of caution about trying to extrapolate anything from this. Looking at this issue through the lens of ethnicity does not do the victims any favours," he said.

[...]

The data was so poor that reliable details of ethnicity were available only in 940 of the 2,379 cases.