I think some wildflowers benefit from being sown in wee pots and then planted as plugs, rather than being sown directly onto lawns.
Another thing that makes a difference is soil fertility. Many wildflowers want comparatively barren soils. Others need bare-ish earth so you'd need to scrape away a bare patch in your lawn.
Another good place for info is the bsbi.org (Botanical Society of Britain and Ireland). People are very helpful if you want to ask questions.
There is a #wildflowerhour on Twitter every Sunday at 8pm too.
Deer eat any "garden" flowers that I plant so I've allowed our garden to revert as much as possible to what we think it was before our house was built in 1890 — cow pasture — and, so far, have identified over 200 wild plants (including mosses and liverworts; it's not all flowering plants) in it without planting any. I let thing set seed and scythe afterwards. It has been an amazing learning experience.