Yes IPAs are probably meant to be a bit more bitter than special bitter or best bitter and a lot more bitter than mild. However there's so much variation in draft British beers that I never really noticed the difference. I can definitely tell mild apart from other beers as it's so much less bitter, and special/best tend to be stronger (4.2-4.5%) than regular bitter (3.5-4%), which can sometimes taste watery.
These days things are changing as US style hops are very popular and there are lots of new pale ales and golden ales that use them. British hops tend to have far less aroma/flavour but character from the yeast makes up for it a bit. Also the water often has high mineral levels - probably more sulphate that typical US pale ales.
Hope yours turned out well.