I'm sorry to hear of your situation, and although I am not as familiar with the health care system in the UK, I would expect that you should be able to request a home visiting nurse and physical therapist to provide lessons and short term assistance in putting the hosiery on and to help you find a way to be more active in a safe manner. In the U.S. those on medicare/medicaid can at least get an initial home evaluation by a physical therapist and nurse to assess your abilities and living situation for safety. Then recommendations for modifications if needed, to your home can be made so that you feel safe to ambulate (even if it is initially assistance of an individual therapist until you get a bit stronger and more confident). There are tools that can be provided to help you put on the hose, etc. Because you are at risk for falling, this is usually something that the government or health system will pay for, as it is preventative and can keep you independent, instead of needing to be in a hospital or care facility. Especially since you have suffered a fall before, this should justify the cost of getting you a walker and short term assistance at least. You are worth asking your doctor to see if you could have a home evaluation. Let them know of your fear of falling and difficulty applying the hose, so that they can order a home evaluation and possible short term physical therapy training and assistance.
Here is a series of diagrams showing the correct way to put on the hose, perhaps this might help in the short term: Double Click HERE
I understand that the pain from the sciatic and your feet can discourage you from walking. But walking and exercise is so very important to our basic physical functioning (it keeps the heart strong; helps to pump fluid from the extremities back to the heart, etc.) that it is very important that you do persevere in practicing some sort of movement. Perhaps consult with your doctor on a pain medication, or even consider taking an over the counter pain medication about an hour before exercising, as this may be all you need to make it easier. Even if you can only do some flexion or mild 'bicycling' exercises with your legs while laying in bed a few times a day, over time this will help some with the swelling, but more importantly, will help to keep the muscles from wasting, not only your legs muscles, but your heart muscles. Don't pressure yourself to do too much in the beginning, but do a little each day, and you will start to get stronger and be able to do more, and eventually you will see more and more results from your effort.
If there were a way for you to do swimming, this would be an ideal form of exercise for you. If there were a way for you to participate with others in a similar situation as you, in an exercise program, this too could be very motivating and encouraging for you.
Sometimes too, when people have these sorts of pain issues and history of falling that results in them being fearful of trying new things, a medication such as an SSRI can help to get you motivated to start moving again. Not only can it help you to over come your fears, but it has been discovered that these medications, which were developed originally for depression and anxiety, also help with nerve and peripheral pain (which of course sciatica is a nerve which is irritated, and your feet pain may be nerve related peripheral pain. You may want to ask your doctor about this as well.
Let me know if you have any questions about any of these suggestions. I hope that this discussion will help you to ask for more help from your health care providers. You might not be aware of some of the programs that are available to help you. Often one has to be assertive and even a bit demanding to get the help that is their right.