Check all the door, boot and bonnet switches for integrity and corrosion - these are frequent places for alarm gremlins to start.

Make sure there's nothing loose, flapping around inside the car.

Read the owner's manual - find out if there's a procedure to set the alarm but excluding interior sensors and find out if the alarm still goes off.

Check the condition of the alarm backup battery, if that's on the way out it can cause alarm triggering.

Check the alternator charging rates and main battery connections as that can do the same.

Thanks for prompt response RT, will look into it all.

There is nothing loose/flapping in car, but I heard of a spider triggering a car alarm once, sounded like total BS to me.

That's not BS - I've been called back to offices 30 miles away at 3am because I was a keyholder and the alarm had gone off - turned out to be a moth !!!

Abject apologies for casting aspersions on your suggestion RT, I totally believe your story about the moth, but I doubted the spider thing.

I promise to think before rushing to the keyboard in future.

Apology not necessary - challenging things is the way we all learn more.

Thanks gordonbennet, advice appreciated, but I capitulated as the problem was driving me nuts.

I took it to a Fiat dealer who dignosed it as water in the loom, I must say I didn't get that, I'm not mechanically minded at all but I'm reasonably sure that a loom is a kind of junction box for electrical wiring, and water and electricity don't mix so why haven't I had some major electrical malfunctions, apart from the alarm?

Anyway the audible part of the alarm has been disconnected and I can lock the doors with the key fob again and mine and the neighbours sleep will no longer be disturbed.

Naturally I will have to throw myself on the mercy of my insurers and report this, and hope that they don't jack my premium up too much, maybe I'll just forget that and part ex the Croma for something else.

An interesting aside to all this is that 4 weeks prior to visiting the Fiat dealer I had had a service and an MOT at an Italian car specialist who has serviced all the Fiats, (5 or 6) that my wife has owned.

On picking up the car from the Fiat dealer I was informed that they had checked the oil and it was low.

I had to pass the Italian specialist on the way home so I drove in and told him about the oil.

He said, "Let's have a coffee Frank and let the engine cool and the oil settle in the sump." He then popped the hood, took out the dipstick, wiped it and replaced it, pulling it out again to show the level to be spot on maximum.

He said, "They just hope that you'll say top it up then, so they can get more money from you."