it depends on damage so cant really tell without a picture, but for a proper repair as it will be week in that area it will need bracing for strength, various ways, but drilling holes either side of the cracks and then roughing up inside of bumper for a good key, then fibreglass it from inside. Then filler from outside
any products similar to these will be fine like body filler/p38
http://www.ebay.co.uk/sch/i.html?_fr...+piller&_rdc=1
fibreglass/p40
http://www.ebay.co.uk/sch/i.html?_od...iller&_sacat=0
availble from halfrauds aswell