Is your alarm making your life a (short term) misery? .. Kill it 
Having read dozens of acquired a 2005 megane 1.5 dci dynamique, i have noticed it has the dreaded problem of the alarm sounding a minute later after being locked.
i am amazed to find that NO ONE has actually posted a semi-permanent fix for this problem.
I have read posts on temporrily disarming the alarm by pressing the start button 5-10 times and pressing lock after which should result in 3 or 4 beeps.
This didnt work for me. And even if it did, you have to do this every time.
After rummaging around in the boot - i found the alarm unit, disconnected the wire, and hey presto - no more sodding alarm.
Yes, the car no longer has an alarm when you do this. But i for one, havent got the time right now to be buying sensors, fitting them to find its not the problem, and tracing where the problem lies.
I can imagine if it was a cold dark wintry night, and you had the snuffles with a hint of fever or manflu, the last thing you want to do is spend hours and hours taking the car apart so that you can lock it safely and get into bed, or sit unlocking/locking the car from inside the house all night in efforts to keep the peace with your neighbours.
Even moreso because this is now less than £1000 worth of vehicle - Fixing the alarm problem properly would not result in any increase of value to this vehicle.
And quite frankly, if Mr Theif wants to steal this cheapy renault megane, then more fool him. Why would you bother ??
As for break-ins - the alarm is fairly gentle sounding anyway, so it wouldn't scare of a thief, until they have taken what they were after. In which case having an alarm is pointless IMO.
Sorry for the long spiel, but you get my drift , im sure you do.
WITRHOUT FURTHER ADO........THE FIXSo........... as a semi permanent fix, follow these steps below as i discovered
OPEN THE BOOT
LOOK TO THE LEFT SIDE AND UNDO THE CARPET WHICH IS TUCKED UNDER THE TAILGATE RUBBER SEAL
FOLD THE CARPET BACK AND YOU WILL SEE WHAT LOOKS LIKE A CUBBY HOLE, WITH BOLTS AND SCREWS IN THE VICINITY
HAVE A FEEL AROUND AND TRACE THE WIRES THAT YOU CAN SEE TO THE ALARM UNIT. THE ALARM UNIT SHOULD HAVE A RED BLINKING LED ON IT.
FIND THE BIG PLASTIC CONNECTOR - UNDO THIS CONNECTOR
THAT IS IT.
NO MORE ALARM !!! - BUT YOUR REMOTE CENTRAL LOCKING WILL STILL WORK AS NORMAL AND YOUR CAR WILL START UP FINE
(THIS OBVIOUSLY HAS NO CONNECTION TO THE IMMOBILISER WHICH WAS WHAT I WAS AFRAID OF)
Now you can wait for a summery day when the birds and the bees are singing/tweeting at their hearts content, to plug this back in, and find the real cause of the problem. I for one will not be doing this, ever! (Life's too short to waste time)
If you do want to do this, here are what i believe to be a few common faults which cause this problem:
- ultrasonic sensors in pillar C (behind/to the side of the rear head rests)
- bonnet pin which tells the alarm if the bonnet has been opened or not (i armed the alarm with bonnet open and got a constant solid beep which wouldnt go off, so i dont understand how this could be the cause of SAID problem without it beeping like this - but its what i have read)
- door sensors (i believe to be in the locking catch)
- sensors in the rear view mirror housing
- Boot sensor , similar to the bonnet sensor , but also in the lock/catch i believe.
i hope this helps many people - as this wasted about 3 hours of my time today.
JUST DISCONNECT THE DAMN THING AND GET ON WITH YOUR LIVES !
ENOY !

(If anyone wants to make a nominal donation for this piece of information - paypal
s4k1b@hotmail.com - cheeky i know - whilst i dont expect anything at all and really dont give a flying monkeys - all the 1p payments i receive will be a testament as to how many people i have helped which will be very satisfying ! I doubt i will be coming back here to check updates if im honest, however i do use paypal weekly so will be kept in the loop via this)