Canasia Sports

My girlfriend is looking for a mountain bike so she can do some basic riding with me, it'll mostly be fireroad trails, possibly tarmaced trails with a little off-road.  She requires a 14 _frame_. She's looking to spend around £300 and I spotted a Carrera Vulcan 08 with an ok spec for £279.99. http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_100... I asked in alt.mountain-bike and someone suggested an 06 Trek 4500 which has V-brakes and a shimano gear set. http://www.paulscycles.co.uk/products.php?plid=m1b3s24p473 Can anyone give suggestions on what to go for, I know that Trek is typically a better brand than Carrera but I'm not that bothered by brand names TBH, plus the Carrera will come ready to ride which will save me some hassle building the Trek.