I'm not sure you can say that with certainty... no overt engagement yes... no engagement - very doubtful.
It is not that likely that the Revolutionary Guard had any direct engagement with British or US Forces (at least not in Iraq). They were largely intelligence and training officers who were (and probably still are) supporting various militias and insurgent groups.
The Shia Militia didn't always get on with them and the Iranians certainly had their people deployed too - it is unlikely they just took a back seat approach especially given that they used the offer of stopping killing British troops in return for the UK backing off their nuclear enrichment program.
Without going into too much detail....There is some evidence that Iran was effectively supporting The Jaish al-Mahdi in Basra, however it is not as simple as stating this is evidence for overt attacks by Iran on the British. The Mahdi Army were a Shia paramilitary force who opposed what they saw as US occupation of Iraq and Muqtada Al-Sadr has close ties to Iran (primarily due to his Shia affiliations) however he certainly was not a supporter of the Iranian Govt and definitely not of Iranian interference in Iraq. The Mahdi Army were as much at war with rival Shi'te factions such as the Badr and Sunni Insurgent Groups such as Ansar al-Sunnah as they were against the coalition and equally Iranian interests were in supporting Shia factions rather than opposing Coalition troops per se, Iran supported all kinds of groups who were opposed to Saddam Hussein before the Iraqi Wars. Iran has a vested Interest in Iraq and it is to be expected that it would support any faction that serviced those interests, which is precisely what we and other countries do across the world. In fact there is more than enough evidence to suggest that the CIA and other coalition security forces have been involving in cross border 'paramilitary' attacks on Iranian positions, including US support of Sunni Militias within Iran. So again quid pro quo.
IEDs in the form of artillery shells often couldn't penetrate armour... strangely enough IEDs identical to those used by Hezbollah started turning up. I've still got a rather gruesome photo of the remains of a car containing two bodies of some silly individuals who hit a pot hole in a road while transporting them....
Hezbollah were training Iraq Militia so that is not really surprising and again, if we are to look at Iran we must also look at Syria and particularly South Africa.
Erm no - that's just silly - my original post was in reference to a comment that Iran has never attacked us - I'm not advocating military intervention against Iran on that basis. (If there is sufficient evidence of a nuclear program then that is a different story...)
I agree, given significant and incontrovertible proof of a Nuclear Weapons Program then the situation needs to be reassessed. However, Iran is primarily a defensive Nation and if we (namely the United States and Britain by association) did not have an interventionist foreign policy in the middle east then Iran would not see Britain as a thread to it's security.
This is the problem with the middle east, it is not as black and white as the media and US senators would have us believe.

