elDuke - Chav is the term for the social underclass of Britain. Please see
www.chavscum.com for further details. 'Chavtastic' means that the body kit would appeal to these people because it lacks taste and therefore would appeal to many of these people - as can be witnessed by a) their 'designer' (if knock-off Burberry tracksuits can be classed as 'designer') clothes, b) their taste in jewellry and c) their names.
Personally I think the chavscum website is in poor taste - it pokes fun at the social underclass who know no better... and, what is most sad, don't aspire to anything.