Hello there, thankyou for the tag MuppetGirl
The funding you are entitled to will vary depending on what course you are applying for. As an example, people applying to medical courses can apply for an NHS bursary to help with the cost of living and materials.
Other courses will enable you to apply for the full tuition fee loans and a maintenance loan and grant (means tested, but if your family is low income you should get the full amount) .
CCUK has a students grant which is available to people who have additional needs due to UC or Crohn's. You will need to get evidence of how your condition creates an extra need but this is pretty straight forward.
Applying for the disabled students allowance can be done at the same time as applying for your student finance. They will also ask for evidence and may ask you to go to an assessment. This assessment is not there to catch you out, they use it to work out how they can help you (for example, meeting the additional cost for living somewhere with an en-suite).
I would say that it is best to be honest with your university. My college tutor actually mentioned my (at the time undiagnosed) illness in my reference, she used it in a positive way to show my commitment and perseverance, showing that I had achieved high attendance and good grades despite being constantly ill and having lots of hospital appointments.
The university course I was going into was very physically demanding, so I'm not sure how it works for other courses but we had health questionnaires to fill out and had to pass health checks. Again, this is not there to trip you up, its there to make sure that your needs are met. It may be that the university can offer you accommodation that is suited for your needs at a lower price or give you priority for that type of room. University accommodation is always allocated on a first come first served basis so it is really important to get your application in early and let them know of your extra needs. My university allowed me to have a fridge in my room at no extra fee to make sure I had somewhere to store food (I'm gluten intolerant and cant mix my butter etc) and somewhere to put my meds if needed.
Another option is to look for private student accommodation. Depending on where you are looking to study this can be significantly less expensive than going into university halls. The downside is that you aren't on-campus with the other people on your course, but its pretty common for people to travel into university so you wont be the only one.
Another reason to be honest with your university is so that they can get systems put in place for if you are struggling, such as extensions on assignments if you've been very rough or in hospital, extra time in exams and the facility to use the bathroom if needed, and they can get something on your record to stop you being penalized if your attendance drops.
Honestly they won't hold this against you. My university was brilliant with me and they did everything they could to help and allow me to progress. A few months into my first year I had to leave because I'd deteriorated significantly and the university gave me a place for the next year - no need to reapply - and then they did it again the year after. Unfortunately I haven't been able to take up those places because my health just hasnt been good enough and occupational health haven't felt it would be safe. The university have made it 100% clear that what has happened will not impact any future applications to the university and that I will have the same chance as everyone else. I was applying for a nursing degree, which is always hard to get into and the uni were prepared to help me provided I wasn't putting myself at risk. Any good university will do everything they can to help you, and your illness won't put them off, if anything it will show them how much you really want this.
Good luck, please feel free to message me if you'd like to chat in more detail.