Cyclocross frame size question
Can you step over the top tube without doing extreme acrobatics?-- if so, the height shouldn't be a problem; The length of the top tube (i.e. how long the bike frame is rather than how tall) is the more pertinent question. I can't say either "yes" or "no" to "is this frame too big?" in this regard because people's dimensions vary widely anyway: I'm also 180cm and supposedly have relatively long legs according to some "professional bike fitting charts" (but I doubt that my legs are in fact longer than most &mdash; see e.g. a sizing chart from ebicycles) for someone my height and most 55-56cm top-tubed frames fit me more or less okay but your legs may be shorter or longer than mine, meaning you'd need a shorter or longer frame length to accommodate it.

If you can't get (unbiased) professional fitting advice, try doing some "real" riding the bike and see if the posture is comfortable, especially when doing turns (both leaning-style turns and turns using the handlebars): If it fits reasonably well and the price is good enough, you can easily tweak the dimensions using handlebar and saddle adjustments and/or replacements.