1) are there any (dis)advantages of a solid dish over a mesh one?
Yes, it has no holes in it.
2) I want to be able to receive either astra or hotbird, what LNB would you recommend? will one off a sky minidish work?
You'll need a "universal" LNB to suit the dish. If your dish is oval (much wider than it's height) then a minidish LNB will be perfect. Otherwise it will be a poor choice.
3) I'm going to the electronics store tomorrow, what type of cable do i need to connect this all up, i.e what is it called?
75 Ohm double-screened coaxial cable using copper (not aluminium) foil.
See review at
http://www.netcentral.co.uk/satcure/cable.htm