I personally wouldn't go on a gap year if you don't have any solid plans on what to do, job opportunities this year are looking a bit scarce, as is travelling without the fear of the gov suddenly announcing you need to self-quarantine when coming back.
Out of interest, what course were you originally thinking of doing?
I'm going to start my undergrad for single honours history at Warwick this September and I got pretty similar grades to you. Part of me did think I could have been more ambitious and applied to more top unis in my original 5 choices but I wouldn't have gone for Durham cos too far. Much like you, part of me did wish I should have applied to Cambridge, it wouldn't have hurt. But on second thoughts I'm not sure if Cambridge would be for me 🤔
Obviously because I haven't started yet, I don't know how academically stimulating the course is but I don't think employers wouldn't really distinguish between Warwick and Durham. As you said, Cambridge would probably be a bit different...
Best of luck ☺