I’ve found the Extra service stations excellent, I often stop at the Baldock one on the way back from Twickenham especially since Ed’s Diner shut down at South Mimms. There’s a great independent noodle bar there that serves excellent veggie noodles. I’m also a stone’s throw from both Cambridge and Peterborough Extra’s, both handy to pop into for decent food (well as decent as you can get from a service station) on the way home.