Who is the leader of the England government?

With a constitutional monarchy the Queen is the head of state and her assent is needed for forming a new government - although this is not of much real impact all Members of Parliament do swear an oath of allegiance to the monarch

Control of English Government

The British government is run by the Prime Minister, currently David Cameron. He is head of the administration.

• Theoretically the leader of the elected party has the position of Prime Minister, and he presides over a Cabinet of Ministers of various departments, health, education, defence, etc. The Cabinet discuss and formulate government policy then recommend their decision to the House of Commons, formed of elected members from all over the UK. 659 members of all parties. The House votes upon the recommendation and if it is carried it becomes government policy if it is defeated it does not. (Most measures have to be passed by the House of Lords, too).

• In practice the elected party has a majority of members (called seats) and so the Prime Minister is usually able to ensure that all items are passed, although if the opposition parties members can combine their votes it may be defeated. A defeat in the House of Commons usually only happens if some members of the governing party rebel.

It is possible for a minority government to hold power - one where the largest party does not have an overall majority in the House of Commons - but these seldom last and are ineffectual unless they can broker a deal with one of the other parties.

The only right of the Queen in the UK according to the Ministry of Justice, is the right to be consulted. In practice that means the Government is legally free to ignore her advice. The Queen is still held in great respect by the people so the Government has that to consider if her displeasure becomes known.

That last part isn't true. The royal family isn't particularly popular. Furthermore, they are expected to stay away from politics altogether. (Having said that, Prince Charles does make public remarks from time to time, usually in support of organic farming or something similar.)

Control of power can depend on a number of factors. Officially all power stems from the Head of State, the Queen, although her powers are mostly viewed as ceremonial. Since Peel in the 18C the position of Prime Minister has been the most significant one and it is the holder of this role as leader of his party, who is responsible for key appointments and for chairing the Cabinet which meets daily to decide policy. Limits to the power of PM include a small majority in the Commons, which makes him prey to factional influence from his and opposition parties, economic conditions and personality. Since the early 20C the PM must be a member of the Commons and therefore there is also a leader for each party in the second chamber, which is the House of Lords.

At different times and under different circumstances the limits to the power of the PM are also varied. Mrs Thatcher from 1983 had a substantial majority in the Commons and a forceful personality. She was therefore perceived to be very much in control. The previous PM had been James Callaghan who led a minority administration and could not impose his will on a Labour party riven by factional fighting. He is therefore seen to be a weak leader. Other factors can include external politics - Eden's position was fatally weakended by US opposition to the Suez crisis.

In previous decades one constant in Govt was the Civil Service and arguments have been made that true power was vested in this body. Since the 80s this has been eroded by the prevalence of political advisers to such an extent that now this group is identified as a power in itself. From this stems the criticism of Alistair Campbell under Blair and to some extent (because he is not voted into office but ennobled for political reasons) Peter Mandelson.
The government, with David Cameron as Prime Minister.