Just wondering if anyone had any ideas how I can overcome this... Our 6 month old pup is petrified of being brushed, although quite happy to lie next to another dog being brushed. Just the sight of a brush sends him in to a panic. He's a long haired breed so it's inevitable that he will need grooming.

How long has your pup been like this? what kind of brush are you using? I start pups when they first arrive with a (human) baby brush so that it feels light, perhaps you can try a grooming mitt so the pups feels like it is being petted?  hold a special treat in one hand and allow the pup to nibble treat whilst you touch the boday with the brush with brushing movements.
if your pup has been like this for a while you will need to go very gently.

avoid a brush.....and use a comb?

I wait till they are tired out and lying asleep on my lap or the sofa and gently run the soft brush over them,play with their feet in preparation of nail/paw trimming and they get used to it and build on it from there.

What about one ofthe zoom groom mitts to start with? And try doing it after a good long walk rather than when tired. Somedogs really hate being interfered with at that point.

Try squashing some corn beef onto the tips of the fingers not in the mitt to help with positive associations.

If that doesn't work take it back further. Have the brush next you and everytime you turn the channel on the TV pick the brush up turn it over. Dog doesn't respond give a reward. Gradually move the brush nearer to the pup and hold it longer and build up to a single stroke and reward. Build up over time to a full groom,going to take sometime to achieve.

We have a Pom who won't let us do her claws.  My mum holds her, my dad gives her big chunks of meat to chew at whilst I clip them.  Maybe you can do the same with your dog?

Thanks everyone, that's been very helpful :-)

Eeyore, try this test: use the brush on your own head and see what it feels like. Slicker brushes and coated dogs are easy to misjudge unless you try it yourself. I generally use a series of Spratts combs, working down to the finest toothed comb, and the brush they all like is my own (or rather it used to be mine :)) boar bristle brush which is a lot softer on them than nylon bristles.

JAY15 thank you, that is good advice :-)
I love your comment underneath your name...I too made the cream carpet mistake :-D

Look on the bright side Eeyore, it keeps the people in the carpet industry in work :-)

I give a nylabone or chew when grooming puppies esp: it goes right back on the shelf as soon as I have finished , pup will let me groom  for as long as i wish as long as he has his bone. (I also have a long coated breed)

All good suggestions, all with the same general theme, it is about desensitisation and habituation. The dog needs to learn that the brush isn't a scary thing! First let him get used to the presence of the brush, slowly over time working towards actual brushing - maybe only a couple of brushes at first - building to a complete groom as they progress.

Treats can make this progress a whole lot easier and the suggestion of using the brush on yourself first was a great idea! That way you know whether or not the dog should be concerned! I know I'd be scared of brushing if it felt awful!