To me this hallway is screaming out for some dado rail height panelling, I would run this all through and up the stairs and, as the stained glass seems to be consistent throughout, pick a colour from this, i.e. a light green to paint the panelling. Then a nice light but bold print wallpaper above the panelling would look really nice. The staircase is a nice example but needs a bit of cosmetic work to tidy it up and a new lampshade and this hallway could look great!

Your hallway is beautiful, but I understand the dark issue! It has made me think about a couple of instagram people that I follow... The first is semi_in_suburbia who had a similar dark hallway and has since painted it. Not sure if this link works, but I will try! https://www.instagram.com/p/Bc4YiUrgx7o/?igshid=1e9433qgiora5 The second one is Malmo and Moss - in addition to Instagram, her hallway transformation is also in a blog... https://malmoandmoss.com/home-1/2019/12/6/03ehb3k5ckvleip5u7tunnvgqnoc3o Both have painted their wood in pale muted colours - and look stunning...

I agree that an 'over the radiator' table or shelf would look lovely, although I think your radiator would look lovely if it were changed to a 2 column old school style one personally, in white. Then a shelf or radiator table over it (as in the photos added by the previous poster). Then some accessories by the ever stylish Kelly Hoppen and a plant, and it will look great. Good mirror by the way.

We had exactly this situation in our current home. We bought the house with the intention of renovating so got rid of the indoor wall and door and built a bench with storage below for shoes and a coat rail. It looks better and is the landing zone for much of the school and work gear now. The shoes are not always I. The press bit easy to put away if someone calls to the door😃. Down side is the porch was an additional insulating layer and cost🙁. Best of luck with the changes and hope this helps.