thanks Geoff,
i'm pretty much counting on the first one or two being failures but its all part of the game i suppose
i guess ill do what every beginner gets away with once.. just getting in there, attacking it then coming running for help when it goes pear shaped
from what i've read, getting the mirror spherical should be fairly straight forward so i'll try for that then ask where to go from there
any recommended supplier for blanks/grit?