The usual route to ill health retirement is to go off sick first.
It depends on your employment contract what your sick pay situation is.
Your employer will probably make up your SSP to full pay for a time and then half pay for a time. At the end of these time periods a decision usually has to be made regarding your return to work. If you are still too sick to return to work you can make an application to receive your occupational pension early.
If you don’t have a work pension there isn’t a state retire early scheme. You have to wait until normal retirement age for your pension. If you are of working age but not able to work due to ill health you have to apply for Employment Support Allowance.
ESA is a very complex benefit but you can get lots of help and info from www.benefitsandwork.co.uk It costs £20…00 a year to join but is worth every penny.
Do you already get DLA? If not the above website will help with a claim for this too.
George has suggested paying off your mortgage with payment protection if you have it. Lots of people fail to do this even when they are eligible.
Other benefits that you can apply for are almost all means tested and will depend on your financial situation such as savings, working partner, occupational pension etc.
A good place to get a broad strokes idea about your entitlements without having to actually see anyone is www.turn2us.org.uk