Secure Document Destruction

My aul fella has about five black bags full of documents he needs destroyed. It'd take an age to do it with a shredder of our own, so we're looking for someone who could destroy them commercially for us. Obviously they need to be extremely reputable, he's not going to hand them over to some guy with a van to burn in a field. It needs to be guys who have been in business for a while, preferably have contracts with some bigger companies who can vouch for them, but are willing to do smaller jobs.