Veronica.. I planted one elsewhere many years ago and never looked back or used it again and totally forgot about their existence. Thanks for confirming. I loved looking at all the wall growing plants all over UK, it's very fascinating to look at and gives me the historic vibes. I miss it there already!

#3 looks like Stylophorum or Chelidonium.

The pink flowers in 3 and 4 are Red Campion, Silene dioica, a native species. The blue flower in 4 is Green Alkanet, Pentaglottis sempervirens. A self seeding naturalized plant with a nasty habit of leaving itchy hairs in the skin of the gardener. The yellow one is a double form of Greater Celandine, Chelidonium majus.

Non native Centranthus ruber is ubiquitous on walls in my area. It comes in dark and light pink and white.

Silene dioica is native to Europe, not here.

Heruga took the last 3 pictures in the UK. Hence 'a native species'.