for removing pads and calipers you only need to remove the 2 x 7mm bolts. It's only if the discs are to be removed/replaced that the 2 x 10mm bolts need to come off.

Haynes advise the 2 x 10mm bolts should be renewed but I queried this with my local vaux dealer who said they just used the same ones. I've changed my discs 3 times and I'm still using all the same bolts.

btw when I say 7mm and 10mm i'm referrring to the size of allen key required to fit the head of the bolt

I did this about 2 weeks ago. In the haynes manual it tells you that you need to replace the bolt but you dont need to. There are 4 bolts you need to remove altogether. i think 2 are 7mm bolts and 2 are 10mm. The 7mm ones are alright as they have dust covers on them. But the 2 remaining 10 mm ones are a biatch to get off as mine had rusted over. But no you dont need to replace the bolts. (sorry bout the essay)

If it is just a case of taking the calliper of to change pads, etc then you can use the existing nut.

I'm going to take my calipers off tomorrow as the brakes are squeking and I've been told to put copper grease on the backs of the pads and the sliders.

I'm sure there is a nut that in the haynes manual says you need to replace after removing. Can I re use the nut? or do I need to get a new one from somewhere?

Cheers