You would have thought this was the easiest thing in the world!
anyway after 1.5 hours trying various offerings i finally found this:
Which does exactly what you want. Simply drag a load of images on it and then resize them!!!!
It does however seem to reduce the quality a little, think i should have started out with png files rather than gifs.
Anyway i now have a way to put an entire presentation including effects on the web.
Simply view it and press COMMAND + SHIFT + 3 and OS X will save a picture to the desktop. Have to give it chance to catch up between shots.
Then can resize them with the above software and then rename them all – need a script for this but am to tired of software nonsense for one night!