Not sure if this will help you

http://www.thegrassseedstore.co.uk/wildflower-seeds-wildflower-meadows-c-30_126.html?osCsid=6da6bdd300a5f1ad132a898823db262c

http://www.countrylife.co.uk/news/article/448136/Visit-the-best-wildflower-meadows-in-the-UK.html

I know they do best on an unimproved soil and that well fertilized meadows are best with the top layer of soil removed, but I guess that wouldn't be practical. If you can get hold of some yellow rattle seed that will help because it is a parasite on grass, and prevents it growing too lush and strong and choking out the flowers. You need to plant according to soil type - not a lot of future in planting chalk lovers on clay. So for starters check out the soil fertility and pH. You'll also need to find any particularly dry or moist areas as that influences what will be happy too.