There are several issues here so apologies for the length of this post, but I hope it will help.
I feel that a lot of people get het up about the native/ non-native issue because of a false analogy with human migration. I've even heard people accuse others of being species-ist! - speaking as someone who's partner's Asian - the issues are unrelated.
Non-native plants are plants that would not grow in this country without humans bringing them. Some are naturalised in that they can reporduce here, others only remain here due to the tender ministrations of gardeners. Some plants like Rhododenron ponticum or Japanese knotweed have given non-native plants a very bad name as they can naturalise and spread rampantly and, becasue nothing much in this country is adapted to eating them (or the things that live on them) they support almost no wildlife. Things like Tulips or can't naturalise as they need human help to reproduce, but still they wouldn't support much wildlife for the same reasons.
Some naturalised species like Sycamores are not great for supporting biodiversity (there are not that many species that can live on them) but are great for supporting lots of biomass (just look up into the leaves of one and they are all covered with aphids). This makes them good for supporting lots of birds, or, like Buddleia or Fennel, lots of butterflies and hoverflies that aren't too picky about where their aphids or nectar come from, and which tend to be the more common species in the first place like blue tits or tortoiseshell butterflies - and this is where the study from Sheffield is coming from - you can get real concentrations of wildlife with some of the non-native species. This can be ideal if that's what you want and, for example, you're trying to get children interested and you want a real 'show' But the more rare stuff, in general, needs native plants.
Rabbits are bit different from plants in that they're higher up the food chain, so their effects are more complex and both positive and negative for other wildlife in different contexts.
The other two issues here are about the miles of transport to get plants to you that are grown abroad (usually in Holland) - the arguments about which are pretty well rehearsed; and about genetic provenance.
If you are going to plant oak trees you can either collect acorns from your local area and plant them - or buy trees from a nursery which does this- or buy them from one of the big Dutch commercial growers. So many trees coming from one source means that the population of oak trees inself loses all its local genetic variation and ditinctiveness, making the trees more vulnerable to diseases in the long term and more 'samey' to look at everywhere you go, the effect is a bit like in-breeding. They are almost as good for the specialist wildlife that lives on oak trees though.
The simplest answer for maximum biodiversity is to use only plants that are native to the area (Beech isn't native in Scotland for example) and whose parents are local plants if you can. But maximum biodiversity isn't really your primary aim here.
You are setting up a nursery, not a nature reserve, and you need to look at health and safety along with educational value as primary concerns. Bamboo is probably not such a good choice just becasue it is easy for children to get cuts and eye injuries from it. Planting bird cherry could also be a bad idea for similar reasons (hundreds of perfect little choking hazards on the grass every year) and it's often found in native hedging mixes. Some old-fashioned rare varities of fruit trees have a lot of educational and heritage value as well as wildlife value and could be a good choice even though they're not 'native'.
Willow hedging sounds OK - especially if you need quick privacy/ windbreak or of the ground tends to be wet. You can probably find someone who makes willow hurdles etc to make you a fence that becomes a hedge as it takes root which can look terrific. Or you could mix this technique with planting a conventional mixed wildlife hedge. I don't know what the right mix would be as it varies from place to place and under different soiol conditions, so you need local advice.
The changes that will occur in the native flora becasue of climate change are a bit hard to predict at the moment, and it is likely to take other wildlife a very long time to adapt, but later on you could consider planting some more tender things like apricots or grape vines if you're feeling adventurous and you're willing to risk them not making it. But I would take into account whether anything would need extra watering after it's established.
You should be able to get good advice from your local Wildlife Trust Conservation department - you might be able to convince someone to come out and draw up a planting scheme for you - or at least a standard list of native hedging or a source of local provenance stock. There's also a charity called Groundwork that may be able to help.