Some bamboos are clump forming and some spread underground and are difficult to contain. If you have the former, no problem.
Re the apple trees, they are probably overdue a good pruning but this needs to be done gradually, rather than just lopping them back all at once. You can go round them any time to remove and dead or diseased branches, but leave any other pruning (such as branches that are crossing each other) until the trees are dormant. I expect they are cooking apples rather than dessert apples, with a sour rather than sweet taste (hence the previous owners thinking they weren't for eating). We make Dorset apple cake with ours, it's a nice recipe and it's great knowing the apples in it were from our tree 
We have no idea what variety it is, but they're lovely when cooked.
I agree with a PP who suggested your borders are rather narrow, you will have much more scope for planting some flowering shrubs if you widen them. Clay soil can be hard work as it is dense and heavy to dig. It's best to add sharp sand and organic matter to it, this will help the soil structure to become more loam. Most plants prefer fertile, well-drained soil so improving your soil will a) ensure you can grow a wider variety of plants and b) make it easier for your existing plants and any you put in to thrive. (Clay soil is rich in minerals but tends to stick together in clods, making drainage difficult. Wet winters + clay soil can mean very unhappy, drowned plants.)
yesterday neighbours had a tree surgeon cut their massive tree back and all the branches fell on our much smaller apple trees Just as an aside, I'm shocked that they did that. They should have been manoeuvring the branches they were removing to fall on your neighbour's ground, not yours!
Magnolia Galaxy can reach 12 metres, is that the kind of tree height you're happy with?