Using flowering plants to tell you when to plant things out

Recently in my gardening groups on Facebook I've seen a lot of people posting memes about signs to watch out for in the garden to tell you when to plant different things out. The meme contains the following information:

• Wait for apple trees to bloom before planting bush beans.
• When the apple blossoms fall, plant pole beans and cucumbers.
• By the time the lilacs are in full bloom, it will be safe to plant tender annual flowers and squashes.
• Transfer tomato transplants to the garden when lily-of-the-valley is in full flower.
• Full-sized maple leaves signal time to plant morning glory seeds.
• Peppers and eggplant can be transplanted when the bearded irises are blooming.
• When peonies blossom, it is safe to plant heat-loving melons, such as cantaloupe.

I don't think it's aimed at the UK or even Europe because it calls aubergines "eggplants". Nevertheless, so far I have accidentally partially followed it this year by planting my broad beans (which count as bush beans because they don't need supports) in the ground this weekend (11/12 April 2020), which is also precisely when I noticed my apple tree's blossoms opening. Mind you, I've previously planted broad beans straight outside in pots in late winter. The pots are to guard against snails. Providing they're protected from snails, they seem to have no objection to being outside in pots from as early as February. This lot started in my unheated greenhouse to give them a boost, but have been hardening off for the last couple of weeks.

I've also planted the pansies that were growing wild in this bed along the edges with the broad beans and I've scattered some mixed annuals there as well, as my broad beans will probably be all over by the end of June and then I'll want something to take over and look pretty.
I reckon it'll be another couple of weeks before the apple blossoms fall.
Edited: By 2 May, most of my apple blossoms had fallen:

Apple blossoms on 2 May 2020

It's been so warm lately, part of me was tempted to stick the runner beans I've been growing in pots straight in the earth already, but I only have 5 and no more beans to grow them from, so I'm highly protective of them. Also, I've let kale flower there because I want to collect the seed, so holding off for a couple of weeks suits me just fine.
For anyone else living in London, I can confirm that as of Sunday 12 April, lilacs are definitely not yet in full flower, as I am lucky enough to have a neighbour with a lilac tree just the other side of our fence.

Lilac tree on 12 April 2020

Edited: as of Sunday, 19 April 2020, next door's lilac tree had pretty much reached the point of full bloom:

Lilac tree on 19 April 2020

Unfortunately all my attempts to grow lily of the valley have so far failed, and I'm avoiding even going out for exercise at the moment, as Joe Wicks's PE sessions have done me just fine so far, but next year I might be able to find other people's lily of the valley (which I understand to start flowering in June) and also their peonies. I do have bearded irises, but I have no plans to grow aubergines or peppers outside. It's the greenhouse all the way for them!