We are called to pray in accordance with God's will and purpose. It is important to share God's concerns, rather than simply praying about the things that we're interested in or concerned about.
The Church & Salvation
This should be our chief concern: that men and women should be saved and that Christ should have a glorious bride for which He died. Everything else we pray about should be centred on these matters. Paul tells us that God "commands all people everywhere to repent" (Act 17v30 ESV) and Peter reminds us that God is "not wishing for any to perish but for all to come to repentance" (2 Peter 3v9).
The Church should be as described by Paul: the "household of God, which is the Church of the living God, the pillar and support of the truth" (1 Tim. 3v15). The Lord is looking for the Church to honour and glorify her Head, and to stand on His truth.
Of course the spiritual state of the nation has much to do with other factors too, so simply to pray for the church and salvation alone is not enough; we need to pray for the right conditions that may bring the blessing of God on our nation rather than His judgement.
Sanctity of Life
Being made in God's image is a privilege but also a responsibility. We have to recognise that God has the final say on our birth and our death. In making us, we are reminded that God "formed my inward parts & wove me in my mother's womb" (Ps.139v13). From conception, God was at work creating us, and no one has the right to terminate that life which God is creating inside the womb.
National responsibility for a policy that allows for the destruction of life in the womb has brought (and will continue to bring) the judgement of God. "You shall not pollute the land in which you are; for blood pollutes the land and no expiation can be made for the land for the blood that is shed on it" (Num. 35v33). Similarly, in our old age or when struggling through illness, it is God Who calls time on our lives, and He wants to give everyone every opportunity to find Him before we leave this world for the life hereafter.
The moral decline seen in the last 50 years in our nation is astonishing. As we have cast His law behind our backs we have reaped the consequences. Broken Britain may be a political statement, but it certainly resonates with where we are in national life. The days of Noah and the days of Lot once seemed so unlikely for our land, but now stare us in the face. The need to turn back to God and to keep His laws and moral standards are the only solution to fix our broken nation.
Time and time again in the Old Testament, we see Israel condemned for following or worshipping other gods. The multi-faith and even some ecumenical movements, while perhaps appealing to our desire to be at peace with one another, go contrary to God's teaching and instruction to us. While it may be politically correct to consider all faiths as equal, this would be to deny the unique and completed salvation through Christ and Christ alone - the grace in which we stand through faith, not of works.
Domestic Policy & Europe
Lawmakers, whether local or national, have a great effect upon our everyday lives - but most importantly, they can affect the spiritual climate of a nation. Laws passed contrary to the law of God bring His judgement; laws passed in accordance with His instructions bring His blessing. God appoints our leaders, whether for blessing or for our judgement. One way God may judge us is to allow other countries or powers to reign over us. While we may be deserving of His judgements upon our land, still our cry can be: "Oh Lord, in judgement, remember mercy!"