So I am a Bitcoin user, I don't mine, I don't have a node, I do keep the blockchain upto date on my PC and leave it open so people can upload it.
I am basically a simple Bitcoin user.  If and when a hardfork is done so that more transactions can be done per block (say 1mb now to 20mb after the hard fork), how will that affect me?

If I only use Blockchain or another online wallet, will I have to do anything, or will it pass me by completely?

Do I just have to get a new Bitcoin QT after the fork? Will my current version stop working?  Will I have to redownload the blockchain (I bloody hope not!).  I have posted this in Beginners as it is a basic question that interests me as a basic bitcoin user and will probably interest true beginners too.