If you are currently working and have unstable angina
. You will need to get a sick note off your GP and will be entitled to sickness benefit from you employer. If your employer does not pay you sickness benefit you will be entitled to claim incapacity benefit/income support from the DWP (department for Work and Pensions).
Furthermore, there is also another benefit you might be eligible for called disability
living allowance. There are 2 different components to this benefit. The mobility and the care component. If you have problems with mobility and cannot walk more than 50 metres without feeling severe discomfort and/or pain eg. breathlesness, needing to use your GTN spray etc. Then you may qualify for the high rate mobility. If you have personal care needs eg. with washing, dressing, unable to cook a meal you may also qualify for the care component.
I am a welfare rights advisor and have been successful in obtaining these benefits for many people in your situation.