325i Over heating

Hi,
I have a 92 325i. Last night, I stopped for gas. All was good. I started out again and all seemed fine. About 4 miles down the road the Check
Engine light came on and the heat gauge needle went all the way to the pin.
I shut the car off and opened the hood. There was some steam but I couldn't tell from where because it was dark. I walked to the store, bought some pre-mixed anti-freeze. I let the car cool down and started to add the anti-freeze. It wouldn't take that much. Maybe a litre or a little more. It was dark and raining and I couldn't tell if there was a leak anywhere.
I started up and headed for home but the heat gauge came right back up within less than a mile. I stopped, called a tow truck and had it taken to a garage. It won't be looked at until Monday.
This is my first BMW, so I'm not entirely sure what I may be dealing with. I have never had any indication of a problem before this, it almost 'instantly' over heated. At no time were there any funny noises.
I'm wondering what some likely culprits might be and how much of an effort to fix these culprits might be involved. I'm also curious as to how likely it is that I may have damaged the head or something else.
I'm assuming that broken hose, faulty thermostat and bad water pump are the most likely causes?
Any thoughts?
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fan or serpentine belt broken/loose.............
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I just went out the mechanic's place. The belts appear to be intact and there's no obvious hose broken (although it does appear that there's approximately a million and seven hoses, none of which are easy to get at ;))
So probably looking at thermostat or water pump I suppose. I didn't really think that either of those things instantly failed. Usually, in my experience, you get some warning that either of those items are on the way out.
Lez Pawl wrote:

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