Fan seems to come on when car is stopped

Hi all, I will preface this by saying that I know nothing about cars, except how to drive them...
For the last few days, each time I park the car, a fan comes on in the engine. It happens after a 10 mile drive, a longer drive and even if I just drive the 2 miles to the shop for milk.
Also, this morning, there seems to be a hole in the exhaust?? It has that really loud sound coming from it (sorry, some of you are probably cracking up at the language I'm using, it's less than technical, I know ) Of could that be the silencer??
It's a 00 Renault Scenic with 79k miles. It's due it's next service at 85k. At it's last service, it had it's timing belt replaced. Not sure if any of the last info is relevant.
Thanks in advance

Maybe the fan is coming on due the engine is overheating?? Probably best off having a mechanic look at it.

have ya checked the water/coolant level.
its the plastic container under the bonnet prob on the right hand side when looking at the engine from the front!

had a similar prob with exaust recently. could be the silencer or the catatitic converter(quite expensive) or the pipe joining all these things together could have a hole in it.
got min welded last week. cost €30. but you could be looking at €200+ if its the silencer or cat converter

thanks for your replies. I'll check on the water first when I'm going home and will see about maybe sending it in for an early service.

Applepie, the fan is electrically driven and controlled by a heat sensor in the water system,even after a short drive in warm weather the water will get to normal working temp causing the sensor to tell the fan to come on,the fan will stay running,even when the engine is stopped until the water is cool enough for the sensor to switch off the fan,how long does it run after the engine is off,bet its only a couple of mins??
As for your exhaust,welding is a good fix if the break is in a part of the pipe where the metal is thick ( most of the pipe is thin,especially if its old and rusty---they tend to rust from the inside out!)
May be better to get a exhaust company to look at,like kwik fit they would probably do you a better deal than an ordinary garage.

Its standard in Renaults for the fan to come on after driving it should only stay on for a minute or so

Thanks folks... it's booked into the garage for a full service now so that should sort it out. The fan only started coming on in the really hot weather we had a couple of weeks ago and we blamed the heat for it.
Then when that strong heat disappeared, it continued, even on a couple of cold nights. So, hopefully on it's way to being sorted!
Thanks for your replies
S