I hope you are still adding to this as I saw some noticeable gaps around the Essex, Herts, London border. I also appreciate space is limited around that part of the map and you can't add everything but the routes fill in quite a few gaps locally and regionally.
310 - Waltham Cross to Hertford (goes through Cheshunt) - Arriva - 4/hr but I wish it ran later than it does.
907 - Cheshunt to Stevenage - Centre Bus - 1/hr - coordinated timetable with 390 - Hertford to Stevenage - also Centre Bus 1/hr. I was surprised to see the really infrequent 38 on the map but not these routes tbh.
13 - Waltham Cross to North Weald - Central Connect - 1/hr
66 - Waltham Cross to Loughton, goes back via Debden - Arriva 1 to 2/hr again ends earlier than it should given that Waltham Abbey is so close to London!
20 - Debden to Walthamstow - TFL - 3/hr
242 - Waltham Cross to Potters Bar - recently taken over by Uno at 1/hr
398 - Potters Bar to Borehamwood - Sullivans - 1 to 2/hr
306 - Borehamwood to Watford - Sullivans - 1 to 2/hr
84 - Potters Bar to St Albans - Sullivans - 2/hr
614 - Queensbury (via Barnet) to Hatfield - Uno - 1 to 2/hr. Also maybe show the 263 London Bus route going from Barnet to Finchley, but that route does goes further south to Holloway.
Also for West of England:
Bristol has buses to Portishead (X4) and Clevedon (X6/X7), a route also runs between Portishead and Weston Super Mare (X5) - All run by First Buses and branded as the Badgerline, it has a very colourful yellow livery and the buses out of Bristol are pretty frequent for regional routes. The X6/X7 to Clevedon is well worth a ride as it's very scenic, doesn't take long to leave Bristol and they usually use double deckers.
Finally, a really good update to this map as I saw it quite a while back (I joined this forum just to give feedback!) and very much appreciated. Finding bus maps for Scotland outside of Lothian is hard but luckily Stagecoach seems to be everywhere, McGills seem to be allergic to producing useful information of any kind about their routes, especially network maps. Finding maps for buses in Wales is literally impossible, which is a real shame given the excellent 1bws ticket in the north of the country. Hopefully it'll be a different story when Wales goes for full franchising. Between this and Bus Atlas, they have been a god send. Sadly most of the country doesn't seem to present bus information in an easy to find and accessible way, surely a major factor in why ridership decreased. No one knows where the buses actually go in their area and if they try them, they get chopped and changed! As lacking as Hertfordshire's bus network can be at times (especially evenings), I am glad we have something like Intalink, I miss it when I am in a different county even though Bustimes is just as useful. It is very useful to know what bus routes are out there, especially in regions that lost their railways in the past, as they are always interesting to explore. Local buses could play a far bigger role in tourism and fill in more of the gaps in our railways if the information was more easily out there.