I'm going to the Lake District in two days (from Cambridgeshire) and only have a day to sort this out if it needs replacing, I think the damage was caused yesterday when I accidentally hit a curb pretty hard. It is the back tire on the passenger side
Yes, get it replaced.
Cosmetic damage to the outside of a tire (or tyre where you are) is nothing to worry about, if there's a bit hanging off you can usually glue it back into place. The main concern would be damage to the materials that give the sidewall its strength. The third picture shows that the sidewall got quite an impact and could be substantially weakened, potentially leading to a failure.
