Like the collect in the Roman Missal, the Common Worship collect (written by the late Michael Perham for Celebrating Common Prayer), is simply a collect for a martyr in Eastertime, because, according to the Companion to Common Worship, we know so little about George. It seems a shame to not have something a bit more specific. Given that the readings refer to the military imagery associated with George perhaps something along those lines might be used – best of all we could just stop worrying about historical accuracy and something about dragons would be great.
How about this from Chelmsford Anglican Mainstream:
We have been taught by the legend of St George
to fight against dragons and to rescue the helpless.
Deliver us, by the truth of the gospel,
from that great dragon who leads the whole world astray.
Free us from our slavery to sin and death
And grant that your light may dawn again on this nation of England.
Through Jesus Christ our Lord.
And from the same source:
The Collect for St George’s Day, in Franz Hildebrandt: Mr. Valiant-for-Truth:
O Lord God of hosts
who didst give grace to Thy servant George
to lay aside the fear of man
and to confess Thee even unto death,
grant, we pray Thee,
that we and all our countrymen who bear office in the world,
may think lightly of earthly place and honour
and rather seek to please [Jesus] the Captain of our salvation
who hath chosen us to be His soldiers,
to whom with Thee and the Holy Ghost be thanks and praise
from all the armies of thy saints, now and for evermore. Amen.