OK. This is my break time and giving beardless students advice on essays is my job SO YOU OWE ME.
"Explain why Islam is important today"
I think the key word is today. You could find out the growth in the number of Muslims over the last 100 years and say whether it is the World's fastest growing religion or not.
You could also link it to globalisation. Maybe the growth of Islam is a reaction to globalisation.
As others have said, you could say whether Islamic countries are located at strategically important locations for the big powers (US, Russia and China). The new 'great game'?
And also in resource-rich areas. The Russian bear dominates European energy supply. The Europeans, therefore, want to increase their influence in the Middle East and Africa. The Americans want to keep Western Europe in their sphere and away from Russia. Is that true and are the current wars in Asia part of it? Is 'Islam' being used as a proxy excuse for an 'energy cold war'?
You could contrast the weakening of Christainity to the growth in Islam and suggest reasons. Christianity subverted by business 'ethics'?
You could also contrast the Shia and the Sunni and explain the schizm and why/how it resurfaced in the 1970's. If indeed it did
The last thing is migration. Christians have migrated around the World for centuries and
we didn't complain about it. Now Muslims are migrating towards us and we're horrified.
So, find out the emigration of Muslims into the UK and connect that to the amount of focus that Islam gets in the media. Maybe the media's interpretation of current events (in pre-enlightenment us and them terms) has given too much attention to 'foreign' religions?
Lastly, compare the media coverage of Islam to that of other religions to see if there is a difference.
Good luck