If ISIS was a recognised military establishment or political party then I'd suggest diplomacy, but they are a cult, like something from Mad Max but worse. You can't wave a white flag and meet for talks, there's no option. If talks were to be attempted it gives ISIS recognition which it does not deserve in any way. I don't think there is one way of defeating ISIS, I think it will take a number of tactics.
One obvious and easy answer is to drone strike ISIS strongholds which we know of but then there's the risk of civilian casualties. I also don't know how much of an impact it will be, there are several ngative possible outcomes. This may kick the hornet's nest and provoke ISIS to carry out further civilian attacks in Europe. It may anger members further giving them the best recruitment tool they need. Learning from recent conflicts in the Middle East whilst ISIS can be destroyed it will probably be replaced with a similar cult.
In an ideal world and what I'd love to see is ISIS being toppled with minimal casualties to innocent civilians and for a democratic regime to be set up in Syria. However, learning from our lessons in Iraq, this will not work. I am not going to be Mr popular with this thought but I think the only realistic solution is to carry out airstrikes and fund local militia to defeat ISIS. Once ISIS has been defeated then for a strong leader to be put in place. I don't agree with the principle but the Middle East is massively different from Europe, there are so many conflicting tribes and wings of Islam. The locals have grown up under leaders who have ruled with an iron rod. I am not suggesting that this should be the future in fact I think the ME should be as democratic and liberal as the West, I just think it will take a century for this to happen.
I do not have an obsession with Corbyn and I don't read the Daily Mail, I can work out from my own findings that he is a danger the national security. I actually watched his interview on the BBC earlier which prompted my comments about him. Today the UK government has given the go ahead for Special Forces and the Police to shoot to kill which I think is a reasonable and realistic tactic to prevent a terror attack. Whilst there's the risk of another Jean Charles de Menezes incident occurring, I don't think there's any other rational approach of tackling a gunman or suicide bomber. Corbyn's approach would involve casualties to innocent citizens, something he doesn't seem too concerned about. He seems awfully concerned over the welfare of ISIS members rather than the safety of our nation.