As Graham says, you can't go wrong with an Iwata but the cheapest Iwata, the revolution CR I think? as per Grahams link, is just over £100.
If your £100 budget is for both then you can get decent starter kits for that plus change, Spraymasters stuff is very good, I have one of their brushes and my initial setup, like most, came from eBay, 2 brushes, (one gravity and one suction) and one compressor for £60 ish which is plenty good enough.
Spraymaster High Detail Gravity Feed d/a
Airbrush Kit on eBay (end time 24-Sep-10 14:37:32 BST)
Link above is an example and the Spraymaster range of brushes are well built and solid, if you do an eBay search though theres plenty of choice.