OP I had exactly what you had and I couldn't believe how successful in 1 or two years I was in increasing pollinators and the natural food chain and it really made me SO happy (and I learned so much in the process). I am lucky in that I was yearning for a sort of country-ish look and feel, and lots of plants that fit into that aesthetic that are hardy, disease free and attract pollinators.
Malus evereste (crabapple) is small, pretty and birds love it. I also planted a rowan by my gate - for good luck - it's still a small tree fully grown but would take thirty years to do that and can be easily pruned on the way.
I read a great book called 'brilliant and wild' which recommended nepeta I think walkers gold or similar. Also bees LOVED chives and oregano.
Climbing roses - try and not spray them as greenfly attract sparrows! I was just sitting on my patio thinking how lazy i was not trying to reduce greenfly (i only ever spray them with a drop of washing up liquid in water and just remove the worst with my fingers anyway) and then a cute little bird just flew over my shoulder and started eating the greenfly! Apparently a huge source of food for them.
Hardy geraniums are easy to look after and bees LOVE THEM. I had wargrave pink but looking it up now I can see it might be considered invasive.
verbena bonariensis made my garden a riot of butterflies in autumn.
Also I really left my lawn to be a riot of daisies and buttercups, I mean I cut it but never treated it with anyone weird.
Was SO PROUD when i discovered some newts as well as the increased bird life. It really is 'if you build it, they will come'.