>Here are a few more for your collection (words that should be opposites, but aren't):
>
>Patch and dispatch
>Sign and design
>Mean and demean
>Base and debase (or abase)
>Liver and deliver

Ah, you beat me to this one. My next tagline was supposed to be "You can't deliver something that wasn't livered first."

>Pair despair (ok, that's abit of a stretch)

IMO, not a stretch... the des- and dis- is just another type of un- prefix, as in

engage - disengage

>Vert and invert

I've only had the time to sift through an abridged (which is the opposite of bridged, I presume) dictionary, looking for verbs on re-; sifting through de-, dis-, des-, un-, a-... would bring us another few strings of pearls.

>and here's one you missed
>
>Bate and rebate
>
>Also, if inflate means to grow and deflate means to diminish, why doesn't 'flate' mean to stay the same.

My language isn't immune to this - we have a lot of words deduced from lost roots. For one, "izlaziti" (to be going out), "zalaziti" (to be setting (sun, moon) or to be getting into), "prelaziti" (to be crossing over something), "nalaziti" (to be finding) and a few others, plus their finite pairs "izaći", "zaći", "naći", "preći" (to go out, to set, to find, to cross) all stem from a verb (or another continuous/finite pair) which doesn't exist in the language anymore.