Buy a small hand-held steam cleaner and do it yourself.
I would only use stream direct to loosen dirt or remove stubborn stains off the sole / rubber.
On leather uppers apply stream to a microfibre cloth then wipe off, use an old toothbrush to agitate suede with a suitable cleaner, brush suede when dry to improve the nap. Then waterproof the trainers with scotchguard.
If white trainers, use an old toothbrush (oral-b electric is even better) and whitening toothpaste to remove stubborn marks (sole or uppers) or spritz APC (all purpose cleaner like Flash etc) to cloth and wipe off.
Don't forget to pop the laces in the washing machine (preferably inside a pillowcase) to stop them tangling or order replacement shoelaces from ebay if tatty to freshen the look.