Hi,
If you're London bound I just saw this today from Secret London, the Horizon22 Building at 22 Bishopsgate in the City of London. They claim its the highest viewing platform in Europe. Horizon22.co.uk
There is so much to see nearby, if you're interested in the old Churches in the City, see this from the Friends of the City Churches.
https://www.london-city-churches.org.uk/cityevents.html
Plus, holiday lights have started to be installed already on Oxford Street!