I have a cairn terrier 21 months .typical terrier but he goes ballistic when he sees an umbrella.Can anyone give me any help please

Hi Bren,
At what distance away from you do umbrellas disturb him? When you find that out you can practice very steady desensitising him to them by having a friend walk first at a distance where he's not bothered by it, then a bit closer. All the time he looks at it and then ignores it you can praise and treat him. When he starts to react to it (not by barking, but by stiffening, hackles starting to go up etc), both you and your friend stop, you make Smudge "sit" and look at you, then as long as he's being good, praise and treat. When he's being quiet, your friend can move away You want him to learn that the umbrella goes away when he's quiet, not when he's barking.
Good luck.
:)