Siezed brake bleed nipple help

[vmax1974]

Wife told her mate I would fix the water leak into the drivers footwell on her corsa c so a few searches turned up that it was the seal around the brake servo and to do it properly you gotta take the servo out and that means the master cylinder and subsiquendly I gotta re bleed the brakes my worst fear has happened all the nipples are seized and it looks like someone has already been at them with a hammer and chisel and chewed them up so am going to have to remove the calipers and get them out somehow without breaking them in the calipers has anyone got a idiot proof way of doing this without breaking the nipples or could I bring them to someone to remove them for me rears are ok cause I will just change the cylinders also where is a good place to get new nipples