charge them for doing it!
tell them if they want their mail redirected, they are to provide you with stickers with their new address on, and a set of 'redirect' to stickers (as your arthritis plays up if ypu write *wink*) and pay a service charge of �29.00 per month.
if this isn't paid, all mail will be left in a cardboard box in your garden for them to pick up at their own convenience
you could also write on the envelopes 'return to sender' - that way the companies know they are no longer living there. put the new address on it so that the companies can update their records.