Brake Caliper Bolts - 100

[over_the_hill]

I intended to change the front pads on my 114 on Saturday. Unfortunately when I came to undo the bottom caliper bolt, it was seized and a bit corroded
I didn't want to risk any serious damage to the bolt (rounding head off etc.) at that stage so I gave up. Can these be bought separately or with say a guide pin set (probably won't hurt to change the pins as well) or better stil are they just a standard size bolt - 12mm hex head ? length ?
If the bolt does end up getting wrecked while removing it I want the replacement ready to go back in.

Thanks