Separate related links into groups
Tidy grouped related links template

Use a case statement to select the section
Use the second-level section name instead of Travel Advice

This isn't a very nice workaround, but there's only so much
fudging of section names which can be done in Frontend
when the breadcrumbs are set from the same data
Remove the grey bottom border from each related group

This mysteriously evaded the previous commit.
Fix the aria tag for related item lists
Merge remote-tracking branch 'origin/grouped-related-links'