There's a charity called Plantlife which aims to increase wild flowers and traditional meadow habitats. They may know of someone in your area who has a wildflower meadow you could gather seed from. In Herefordshire we have a meadows network with the same aim and, as I understand it, it's important to get seed from the locality as it will be suitable for your soil and climate. When we moved here there were many broad-leaved helleborine orchids but as fertility has declined (the pig slurry is no longer being spread) they've disappeared but this year we found four common spotted orchids where none had been seen before. It's important to reduce fertility to get a good wildflower meadow or the grasses swamp the place. Sowing yellow rattle or, even better, eyebright, achieves this.