I don't pay a massive amount of attention to my gamerscore, but... Weirdly just noticed that my gamerscore on my Xbox is 49765, but Giant Bomb seems to believe my score is 50035

Clearly the Xbox must be the one that is accurate... but how on Earth has GB some how worked out i have a higher score?... and is everyone else's GB account syncing correctly, or is this a common screw up?

There is always some latency between the updates. And things like those scores are updated on the backend instead of a client patch which means Microsoft never announces changes if they happen.

If you have your PSN trophies synced up with your gb account, the total points is both the xbox and the ps3 points together.