As somebody who's from the UK and who's had Crohn's for over 10 years I think my first tip would be to get used to chasing things up. My own experience is that the NHS does not take IBD seriously until it gets too expensive or too dangerous to ignore. So if the Asacol isn't working tell your doctor that. If it's months until the next hospital appointment then phone up because months is too long to wait. Also, unless your hospital is different to any of the three hospitals I've been at, expect referrals, medical notes, etc. to at least sometimes get lost in the system. This is what I mean by chasing things up.
Perhaps I'm being too cynical; I don't know. All I know is being passive with the NHS doesn't get you anywhere. If you don't make your symptoms plain to them, they won't inquire any further; if you don't ask any questions they won't tell you anything; and if you stop taking your meds, they won't really care.
But getting the Crohn's under control is important to your future quality of life. Your symptoms sound very similar to what mine were originally. I had liquid diarrhoea 3x a day, but it didn't appear to impact a lot on my life, energy levels, etc. - maybe it'd have been more obvious if I was an athletic person, which I never was.
Long story short, my Crohn's got worse, but not overnight. It took a long time to get that way and I wasn't on any medication. (Couldn't tolerate any of the mesalazine drugs.) You've hopefully got plenty of time left to you to bosh the Crohn's on the head. It'll never be cured but you can hope for a long-term remission.
Oh yeah, and low iron is easily correctable by oral iron tablets, provided you can tolerate them. If you can't then there are more easily digestable forms of iron (try a search for iron on this website) or, ultimately, iron transfusions.