Thank you for all your kind replies!
The site I mentioned costs less than Â£20 for a year's membership and then you get access to all their guides and resources. I know what you mean about some websites being a con, but honestly this one was very helpful to me and I would say it was worth it. The people who run the site and write the guides are ex-welfare rights workers and some of them also have chronic illnesses themselves.
I did apply for and get IB guaranteed until 2011 without any help, but I found that I was much more confident filling in the DLA forms with
the help, and I found their guides to preparing for a medical especially helpful - for example I had no idea that some visiting doctors make assumptions based on how your home is furnished/arranged. My doctor didn't do this, but there have been reports of some doctors going into rooms in claimants' houses to gather evidence about how they live, etc. Because I was forewarned I made sure that my partner didn't tidy up the house for the doc's visit, as the doc can assume that if your home is neat, you have tidied it yourself! Etc.
At the end of the day it's up to the individual whether they feel that they need help, I was very insecure and worried about the application process so I found it was worth it!