I usually shop in Chain Reaction for helmets etc.
However, I would suggest trying some on in a shop so you know what size you need and what feels comfortable as everyones head is different and everyone has different tastes.
If you can stretch your budget though, get an Urge Endur-O-Matic, I know a few riders who have them and they are soo lighweight and are quite cool.
But as for what you would need, its is up to your personal taste, be it an XC style helmet like a Bell or a Giro, or a piss pot like Bern or similar.