Think you've got to be careful here. Forget what you think of Israel v Palestine:
1) Iran developing a nuclear warhead would be a grave threat to this country and everyone in it. Similar to North Korea.
2) Not only are Iran ruled by essentially a hard-line Islamic dictatorship almost sworn to combat western society and interests, but corruption is assessed to be rife in Iran and they actively work with, fund and supply a variety of paramilitary and terrorist groups. So Iranian development of nuclear weapons would not only represent a direct threat to the UK but also a significant indirect threat in terms of warheads or "dirty bombs" falling into the wrong hands (intentionally or unintentionally)
3) Israel is a friendly state and does not represent a threat to the UK or British citizens on the whole. I think this contrasts significantly with Iran and is something people need to focus on, regardless of what you think of Israel's actions in Gaza and West Bank etc.
4) Israeli intelligence is pretty much second to none in the middle east. If the Israelis think Iran is on the verge of doing something bad, they're most likely right. We are talking about a country that successfully swapped all the phone batteries used by top ranking members of Hezbollah with explosive devices without being compromised. Thats the level of intelligence operations we are dealing with here.....