Welcome to my tale of woe 
A first-hand account on what to to expect if you suffer from long-term illness in the UK, and want to claim ESA:
Basically, I used to do a lot of long distance running, until in 2012 the running led to knee problems. Then from 2013 onwards this turned into serious back pain also, which got progressively worse over the next 12 months. I was living abroad at the time, and since I couldn’t speak the native lingo I had some trouble getting effective medical treatment, because of communication problems with doctors. Yet I really liked my life abroad so I tried to stick it out there as long as I could, despite the pain I was in.
Eventually enough was enough and I returned to the UK in Oct 2014 to seek treatment on the NHS. The NHS were worse than useless. Every new appointment has about a 6 week waiting list. Eventually I got to see a specialist. He examined me for 30 minutes and told me I would be in pain for the rest of my life. He printed out two sheets of A4 paper that had some diagrams of stretches and exercises on them. He told me if I do these they may help a little. Then he bid me adieu. That was the end of my NHS treatment.
So I had to go down the private route - so far have spent £5000 and counting on private treatments and consultations and scans.
During this time I have been unable to work as I am in constant pain, and walking, sitting and standing exacerbates the pain. So there is not really a job I can do, unless there is a position available for someone needed to lie down flat on their back all day and stare at the ceiling (if there is such a job please PM me).
So I tried to claim Employment Support Allowance (ESA). I registered for this in Oct 2014. Now, once you register ESA you will get weekly payments of £75 while you wait to be assessed properly to see if you truly are truly eligible for ESA (ie are declared unfit to work). The waiting list for such assessments are usually in excess of 12 months. The assessments are outsourced to a multinational private company called Maximus (it was previously another multinational private company called ATOS). If after the assessment you are found to be unfit to work you will get an increased weekly payment, of about £100, and they will also backpay you the difference for all the time you were waiting (so for example, if you were being paid £75 a week for 50 weeks while you waiting for your assessment, and then after the assessment were found unfit to work and so were eligible for £100 a week all along, you will be paid (£25 x 50 weeks=) £1250 in backpay)
Anyway, I waited 14 months to be assessed, which happened in December 2015. I brought with me a big folder which contained all the medical documents and scans I had accumulated over the past 14 months. I explained to them, truthfully, that I had been in constant pain for over 3 years, and that walking, standing or sitting for over 20 minutes made this pain much worse.
Anyway, got a call this week saying that I have been declared fit for work. I have been taken off ESA and now must look for work. I find that decision to be quite disgusting to be honest, but what disgusts me even more is when I think of all the others in a similar boat but in even worse circumstances than me, for example a single mother with chronic pain issues with 2 kids to support without well-off and helpful parents to rely on (which, fortunately I have).
So does anyone else out there have experience of ESA/ assesments/ ATOS/ Maximus etc, please share, either here, or in a new thread, and lets see if we can help each other
PS The Guardian newspaper are quite good on reporting on government and state abuses when it comes to ESA and assessment, in the comment section below I will post some good articles on this