I travelled to Watford Junction yesterday, and saw a 378 next to a new
710. I snapped the two parked side-by-side, something that probably
won't be happening for long:
https://www.flickr.com/photos/recliner/49443667886/in/dateposted-friend/

The 378s will be re-liveried to match the 710s.

It's interesting how much sleeker the 710 is compared to the rather
frumpy 378. They're nicer inside, too, with larger windows which
aren't partly blocked by the external displays. Of course, both share
the ironing board seats.