Funky cage...i like it.
Im not sure how much heat mercury vapours make but you may need LOTS of ventilation to have a 100watt going for 12 hours a day, especially for a cage this small(what size is your main cage).
Also......a bearded dragon really needs a 4foot x 2 foot cage minimum. your cage however will be great for the first year or so(unless its bigger then what it looks).
For heating I currently use a ceramic holder(downlight $6 from bunnings)screw type and change globe size to suit the season and temps. Globes are just normal house globes with screw fitting.
This provides all the heat they need.
For UVB another light is needed.
Check this link.
http://www.ultimatereptiles.com.au/c...cf54df8585.jpg
These are good........but..... a cheaper, better and more aesthetic option is a 2 foot flouro holder with a $10 NEC T10 Blacklight(white though). This provides more UVB then anything else. Heres another link
http://www.reptilesdownunder.com/rep...tingtestsa.php
Good luck.