What a lovely project Gerard I agree with Nutcutlet's identifications. Now is the time of year to plant gladioli corms - they can go straight into the garden.
Nasturtiums can be sown direct in the garden about now - the ones in the picture look like the trailing variety (which I much prefer) rather than the more modern bush varieties. They are very easy and will 'just grow'. The leaves and flowers are edible in salads and you can pickle the seeds.
Those dahlias look magnificent - you can buy tubers and start them off now in pots indoors and plant them out when all danger of frost has passed. When the autumn comes you'll have to decide whether to dig them up and dry them off and take them indoors for the winter, or whether to mulch them and hope they survive. Perhaps your grandfather will remember what he used to do
I think Nutcutlet's right and the plant between the steps and the wall in the first photograph is an astilbe - it's a perennial which means it will grow and flower from year to year, it likes its roots in a cool and slightly damp spot and it's flowers in the sunshine - wild forms grow on the sides of ditches and streams.