Last time I checked England was not an actual country that is internationally recognised. If you're looking to form a break-away republic you should discuss that with your MP. When England has a seat in the UN and is assigned an ISO country code then I'll be free to add it to the list. Until then United Kingdom will need to suffice.

As a point of order your country is officially known as Great Britain and has the ISO country code of GB and GBR. I was asked to change that, because it was objectionable, to UK. If you don't want Scotland, Wales or Northern Ireland as part of your country why do you keep them? Cut them loose, I'm sure they wouldn't mind.

The flags are nothing more than visual representations of the letters UK and nothing more. I'm not going to have ethnic flags or provincial or state flags or the logo of your favorite football club there. If you want an English flag then add it to your signature so everyone knows your tribal affiliation.