I have to confess feeling a little conflicted on the topic of wildflower meadows; on one hand I totally buy into the romantic notion that it would be brilliant if we could reinstate great swathes of the British countryside with expanses of native grasses dotted with our native wildflowers. However, being a pragmatist to the last I see several major flaws in the plan: - having lost 94% (who counted that?) of our original meadowland, its unlikely we can really find much spare land to reinstate - especially if we need a commercially viable option - food production pressures have never been greater so this is in conflict with the romance - recreating wildflower meadows is not that easy as they are happiest on poor soils. Get the conditions wrong and you just end up with a weed patch (see rosybee trial wildflower mix year one!)
If you accept point one above, then we either do what we can or find alternatives. My view is the latter but I guess it depends on your objectives. If you want the pastoral image then you will need to work hard to acquire the right sort of land and then after several years of careful treatments to remove the plants you dont want and cultivate the ones you do then you may get something approximate ...and good luck. By the way, dont believe any seed packets or distributers that imply you just chuck in a seed mix and away you go.
If you want to support wildlife then I recommend you study the foods that the critters you favour need and focus on planting the right things, regardless if the effect is meadowesk.
If you want to try and preserve our native wildflowers then you can do that in a garden setting where they do not need to compete so hard with the grass for survival as they would in a meadow. Or, work to eliminate patches of grass and put in wildflower plugs rather ie avoid ploughing or rotivating a big area and this will throw up all the buried generations of weed seed.
So, overall my recommendation is to work out what matters to you and focus on that.