I have been told it is illegal, is it? And why?
Im just wundering here, caus where I come from (Scandinavia) we pick wildflowers, we still have loads of them, so could it be that in UK the reason for NOT picking flowers, is caus you don't have as much forest. Most of it was cut down for farming?

Try a google;

http://www.google.co.uk/search?hl=en&q=picking+wildflowers&btnG=Google+Search&meta=cr%3DcountryUK%7CcountryGB

Some are protected because they're rare. When you pick them you stop the flowers developing into seedpods, so damage their chances of breeding. Don't do it.

http://www.englishplants.co.uk/protection.html

I'm not a gardener but it's something I've always wondered. I did a search and this site http://www.ypte.org.uk/docs/factsheets/env_facts/britains_rareflowers.html seems to be quite interesting.

i think this is the rite answer lol ! coastal shingle and grassland support rare arable plants such as Red Hempnettle, Small-flowered Buttercup and Corn Parsley

Try www.scillyflowers.co.uk for a small firm giving excellent service, growing flowers on St. Martins, one of the beautiful Isles of Scilly. This firm gives local employment to the islanders, and the flowers are grown on site, not flown in from Africa, so the environmental cost is less.

I'm looking to plant some outdoors flowers for winter. Don't want anything too big or shrub like, just a few small potted plants/flowers that will thrive in the cold. Any ideas as to where I could start? Am looking for preferably English plants/flowers please.

snow drops in the green & winter clematis

The Texas Bluebonnet is a type of lupine.
There are many lupines available in the UK but I don't know if any look like the bluebonnet.
Have you tried planting bluebonnets?
Don't know how well they will do there, they might not get enough light there & might get too much water but it might be woth a try.