I think some of the separately mapped sidewalks in here are a bit incomplete - see for example https://www.openstreetmap.org/directions?engine=fossgis_valhalla_foot&route=53.634039%2C-2.815702%3B53.634007%2C-2.815523#map=19/53.634189/-2.814973 .
If it was me, I'd just use "sidewalk=left" or similar here; if you're going to use separately mapped sidewalks you need to make sure that you join everything up.
Best Regards,
Andy