So yeah I have an 11mb savefile and it was lagging and stuttering like mad. I've just opened my window as its freezing outside and too warm inside and now my room has dropped in temperature, my lag has been eliminated lol...coincidence?

...and here i thought this would give an actual fix...

Yeah I know but literally all the lag has gone and it's running silky smooth again...

Did you happen to restart your PS3? Because that is known to temporarily fix the issue.