Two boxes - do you mean one of the cupboard and one for the
bookshelves? What is a good way of fixing these boxes (remember I am
a newbie at this).

I would keep the 2 things separate. Much easier to construct and handle.
Forget doors for a kids' room and go for baskets.
The units won't need a lot of fixing to the wall. You could use metal
plates on the back. See here (3rd one down) and probably available in
the sheds.
http://www.isaaclord.co.uk/prodList.asp?ProdId=111&SubCat=1&Nav1=Cabinet+Fitt ings&Nav2=Brackets+and+Plates
With 4 of these on each, you may not need a back.
As for general construction, screws are easy and the heads will be
hidden if they're being painted. Basically you have 2 sides and however
many cross pieces to do the top, bottom, and all the shelves, and you
just screw em together (but they must be identical, so have them cut to
size). If you get that far, come back and get some help with assembling
the things. If that wardrobe bit is over about 3 ft wide I'd break it
down into 2 separate boxes. Neater, stronger, and a bloody sight easier
to move about.

Contiboard - is this a good material to use? (I am not experienced in
choosing suitable materials). Can this be painted easily?

No, go for mdf.

Doors - I was hoping to have some suggestions on where to get some
doors (at low cost) or how to make them :-)


Carcass screws are good for assembly if you can live with black
screwheads everywhere.
Personally I'd go for the B&Q or Ikea wardrobe and build something to
match for the books. Doors and hinges are a pain if you haven't done
this sort of thing before but you can't go wrong with the shelves. Bear
in mind that the wardrobe bit should have a rigid back or you'll never
get the doors to hang straight


I would go for a B&Q wardrobe but there are three issues:
- They are too expensive for this job. (i.e. £100)
- I'm not sure they will be strong enough to support shelving.
- They are for a children's room so they will get a lot of damage (I
doubt they would be easy to repair).

Cheers, Mark