How to treat scab that cat keeps picking at?

My cat has a scab on her head, below her right ear. She keeps scratching it with her foot, and wont really leave it alone. There is another one a bit lower to it that has healed but this one seems to be bothering her. It had started to heal, but she has scratched the scab loose now.

What can I put on it that will encourage it to heal? I have an E collar, should I use that and keep her indoors for a couple of days? Im loathe to use it, but I cant figure out any other way to get her to leave the sore alone.

YES and YES

Has she seen a vet about the sore??? did it come from another animal??

I dont know where the sores came from, the area under her ear turned red, we figured it was from flea bites since she was late for her monthly stronghold treatment.

So we applied that, and she hasnt had anymore red areas, but she has been itching the previous sores with her foot and now it has become a bleeding sore.

I think we will try the collar, she will hate it though poor love, and if it doesnt get better by tomorow we will take her to the vet..

in the meantime Ive been applying hydrogen peroxide and witch hazel to keep the sore free from infection..

Put some triple antibiotic ointment on it once a day in the morning and put hydrocortisone cream on it once a day at night, as well as using the ecollar. The hydrocortosone cream will help stop the itching and the antibiotic ointment will help it heal faster. That's what my vet had me do for Jake a few years ago when he had sores on his face and paws.

My cat had a scab on her face for two years. I tried all sorts to heal it but she continually scratched off the scab. I was recently recommended Manuka honey and to my surprise within a month the wound has completely healed. 

NO Hydrogen Peroxide or Witch Hazel!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   Too irritating to the skin.   Even in human healthcare (hospitals, clinics) the studies lead them to STOP using hydrogen peroxide YEARS AGO as it was found to be too disruptive to tissue that's trying to heal.   It destroys 'granulation tissue' which is a a type of tissue that's formed during the healing process.   

As you're in the UK I'm not sure what options you have for cleaning these areas or what over the counter ointments you have that would be safe for cats.  I have one cat that periodically gets red spots beneath one ear....he is strictly indoors.   I attribute it to him and my other cat wrestling and her giving him a claw there and then he scratches it.    To clean it I use a special antiseptic from the Vet called Chlorhexadine (it's a type of soap used here in hospitals to clean wounds), diluted.....dab it on to clean (diluted with water) then rinse off....then I will apply Polysporin ointment or Panolog cream (from the Vet).   When it was bad in the past I had to make him wear a cone.   I'd also clip his claws on the side (back claws) that he'd use to scratch that area with his foot.  If you don't know how to do this take him to Vet and have them clip the ends of the claws.