As far as I know v11 is the latest release out for the mini, but I would always go through the official channels for a firmware update and never pay for it. Any unofficial update will void your warranty, and they can easily tell.
If the official update is available for product codes other than yours you can find reliable guides on this site for changing product code and a list of codes that will allow a generic firmware install but bare in mind this invalidates your warranty, a fact which some people have had come back to them when they've then tried to get hardware repairs done.
No worries mate, I have an N97 on v20 and my girlfriend has the mini on v10, they seem pretty much identical and I definitely wouldn't worry too much about updating from there until you have it officially available. From what I've read v21 (and v11 for the mini) is mostly just tweaks to make things all run a little faster so not missing anything too major.
I purchase my mini(unbranded and unlock) with V10 version and then updated on V11 when that update is showing up on OTA. All I say that GPS performence is improved a lot, Now it just take 2-3 min to lock down even in moderately build up area after a cold start..(15 min in V10) and general performence is speed up.. Home screen got a nice animation when you swipe those widget to hide/show.
Linear Mode
