The thin polystyrene insoles that come with most boots are fit only for the bin (or if you are keen to keep them, use them in a pair of slippers around the house, not for hiking). What walkers need is a quality insole (or "footbed") and your outdoor shop probably carries a range from off-the-peg to custom fit with price tags to match. At minimum, sorbothane will give much more cushioning and may be treated to combat smells and moisture. Some people swear by "Superfeet" which are rigid but deeply sculptured to combat "pronating" (excessive flattening of the feet) and cost twice as much. Custom fit footbeds are vacuum-moulded to your feet individually, and as you would expect their price reflects it.
I'd suggest starting with a pair of sorbothane insoles (you may need to trim these to fit: ordinary scissors work fine) and going custom only if you still have a problem.
Be aware also of the importance of the right socks, and (if your feet are soft) drying them out a bit before setting off, either with surgical spirit (rubbing alcohol on your side of the pond) or a soak in water to which you add a crystal or two of potassium permanganate (just enough to make it pale pink). This will prevent problems while hiking.
See also
http://rucsacs.com/nov_boots.php for general advice. In the photograph there, the red insoles are sorbothane, the green/grey ones are Superfeet, both worked well in the battered fabric boots (all mine).
Good luck with your preparations. Don't your work colleagues look at you strangely in your hiking boots?
