On reading the explanatory notes to Section 54 of the said bill it seems that in line with the Council of Europe Convention the UK govt removed dual criminality for offences committed by UK nationals abroad in connection with child abuse, child pornography and child prostitution. Hence a UK national having sex with a 15 year old in France would also be a crime under English Law. Scots Law simply goes even further in stating that any sexual offence is relevant and not just crimes against children.