I've just had another look at the film and I think the blotches are waterdrops. I'm not too sure if I loaded the film on properly but it seemed to unreel fine at the end. Although I guess these being my first ever developed rolls problems are to be expected and I do have some usable negatives.
One more question though, I know that stop bath and fixer can be reused and that I can tell the stop has been used up when the colour changes but how do I tell if the fixer has been all used up? Is there just a roll of thumb that you can use fixer for x amount of times?