Hi CPP1972
Welcome to the Forum! It’s great news that you are planning a hedgehog highway.
I’m no DIYer, but I imagine with both lattice and overlap panels, you would ideally need to build some sort of structure around the hole – maybe using wooden batons on both sides, to avoid weakening the fence.
If all else fails maybe you could dig a channel underneath the concrete base board. Or, apparently you can get hedgehog-friendly gravel boards, if you were feeling adventurous!
If you haven’t already seen it, you might be interested in this:
https://www.hedgehogstreet.org/help-hedgehogs/link-your-garden/
Good luck. Let us know if you find a solution.