Keeping my plants alive...

I have never had any luck growing climbers in pots. If you do want to try it you need something at least 3 times as deep and wide.

You could put a tray under the maple, but you could easily drown it in winter/a rainy spell. How it it getting water onto the paving, its on gravel?

How much you water them depends on conditions. The compost usually needs to just dry out a bit before watering again. If it is damp on top it doesn't need watering. If it dries out completely it is difficult to get it damp again and water will just run through the pot. Stand it (temporarily) in a tray to give it chance to soak up water, but be careful in wet weather that it doesn't get overwet. A really good soak once or twice a week is better than a dribble every day. Mulch on top of the pot is a good help.

I would hesitate to put wildflowers in that kind of garden. You have a display for a few weeks then it looks untidy for the rest of the time. This does not matter in a large garden but would not improve your area. Look out some relaxed looking perennials to plant that will give a long succession of flowering and the bees will be just as happy.

Is the climber pot sitting on gravel? If so I'd be more inclined to dig down and plant it in the ground, it will never do in that size pot and in fact no matter what size it will struggle, would be much better with roots in ground. I have a reasonably successful honeysuckle in a big pot at the moment, it's the only thing that has survived well, all clematis were very poor performers because I imagine roots too hot. Jasmine is doing fairly good in another container at the moment but lots of watering required.

Agree with wild flower comments above, a wild flower garden actually requires quite a bit of maintenance, they are not easy to keep looking good or returning year after year. A few good flowering plants will keep the bees happy, I like perennial geraniums as they come back year after year with no hassle, just need a tidy up when they die down over winter and there is a good selection of colours, small flowering hebe good choice too. You can also get dwarf buddleia (butterfly bush) which is nice in ground or pot and obviously attracts butterflies.

Unfortunate so, much much bigger planter needed if you want to grow a climber and if that's clematis it will struggle with the heat on it's roots no matter what size.

If you want to be insect friendly, try planting some catmint - it has lovely blue flowers, and the bees/butterflies are absolutely mad about it.

Agree also about the sweet peas, they're amazing. I have some planted and they're coming up for the 3rd year in a row all by themselves.

Op. Also consider salvia or lavender.

Your clematis looks like it could be "Countess of Wessex". If it is, then you certainly can grow it in the planter. Ours is in a hole in the ground no bigger than your planter, and surrounded by stone/concrete. It's a slow grower compared to other varieties, it's 3 years old and has only around a 3 foot spread (which is ideal for us). In other words it won't cover your wall. It likes full sun but the base needs to be protected from direct sunlight, as someone else said. It's early flowering and in full bloom now, but will have far fewer flowers next month. Snails love it so you'll need to pick these off to protect the flowers/buds.

We also have a couple of acers growing reasonably well in pots and the shady spot in your garden looks ideal. Water them every couple of days until they're established. Then once a week should be fine. They will grow bigger and won't like to rub up against your fence in the wind. You'll need to move them further from the fence towards your patio slabs in a couple of years.