It turns out tonight that I missed off at least one site- the Churchill Memorial Gates in the Crypt at St Paul's Cathedral- https://www.stpauls.co.uk/nelson-wellington-and-churchill
And I realised the omission in the most surprising way possible- reading the detailed itinerary for the England pilgrimage of the Compline Choir of St Mark's Episcopal Cathedral, Seattle, as I was working out when to go and hear them at Evensong and Compline during their pilgrimage as I need to book the train ticket to London soon. The choice was St Alban's Cathedral, St Paul's or Canterbury Cathedral.
I think I have decided on St Paul's on 8 August.