No, not too late. Use a sharp spade to cut the turf into spade-width strips, then cut transversely every 0.5m. Slide your spade in under the turf, about 5-7.5 cm deep, and you’ll find your spade goes through the soil easily to lift a slab of turf. Repeat.
If you have space somewhere , stack the turves upside down,and in a couple of years they’ll rot down into good soil.
re-seed the lawn with a wildflower/grass mix.
That’s the Rolls-Royce method.
In your situation, I would remove the turf from selected areas, and sow your wildflower seeds. If your wild flower seeds are mainly cornflower, corn marigold, poppy etc, those are wild flowers of arable fields, and need the soil clearing every year. So I’d also get a packet containing things like clover, self heal, birds foot trefoil, daisy, and mix that in.
Leave the grass to grow on the rest. When it’s in full flower, cut the grass right down and remove the cuttings. You can continue to enjoy your flowers.
Next year, give everything a good mow in late April or early May, then leave it all to grow and start cutting again in late August. Hopefully, the plants in the area you cleared will start infiltrating the grass only area. And you can always add plants. Go for perennials not annuals.