Ok....but then it was a fixed point in time that Pete Tyler died, that he died in a certain place and that he died alone.
Rose changed things, and I know brought down the Reapers as a result but, once the normal flow of time was restored things were altered, things the Doctor knew about in advance.
Now it may be that it was a tiny thing (the location of Pete's death and the fact that there was a mysterious blonde with him) but it was a change nontheless, and in fact quite a major change since a large part of Rose's desire to be with him when he died came out from the fact that she hated the fact he died alone. Well he didn't die alone, and we see Jackie telling Rose this so....
Oh don't get me started!![]()
But I think the point is that's not a 'fixed point' - we're talking very specific events which have this property of inevitability - it doesn't just refer to historical events in general which the Doctor alters, it refers to events such as Pompeii, which, even though he tries to help, happen anyway - they are inevitable, unchangeable, fixed events in time - not all events or even, it seems, many, have this property. Rose changing Pete Tyler's death changed the future, but it didn't break this rule because his death wasn't one of these pivotal events.