Neil,
So very sorry to hear of your accident, and wish you a speedy recovery.
I have had a number of big "offs" over the years, and have gone through three helmets as a result, including splitting one down the middle on a curbing after losing traction on a heated street hatch (manhole cover) and high-siding when the tires regained lateral traction after a slide on a patch of sand in the roadway . The most recent was in '94 as the object of a murder attempt. I was cycling at the time, but the accident was not cycling-caused. It did result in a closed-head injury despite my helmet (triple skull fracture, broken nose and teeth, complete free-fracture of the upper maxilla, shattered left eye orbit requiring a number of titanium bits and 13 bone and tissue grafts to make right, broken ribs and a lot of deep-tissue injuries and hematomas). Most of the damage was caused by the assailants' attempts to kick me to death, but some was caused by the initial unarrested facial impact with the tarmac.
I can recommend cycling again, with suitable caution born of experience. I returned to cycling as soon as possible and never have regretted it. It is a passion of mine and my primary and preferred form of outdoors recreation. Interestingly, I found myself riding greater distances and with greater ease after my accidents than before.
Cycling after an accident can take place in many ways, and at various levels of risk and difficulty. Even car-topping the bike to a nearby park for a leisurely ride with the family can recapture much of the joy and excitement of more adventurous rides, while minimizing risk. It is a good way to get "back in the saddle" again after a major "off". Beginning again in a conservative manner will allow you to re-evaluate your desire and comfort levels as you progress. Overall, though, there is much to be said for returning to cycling if possible. The health benefits alone are worthwhile (crashes excepted) and it is helpful to confront and address that which has brought you down.
As you can imagine, I endorse the use of helmets and have always used one since they first became available in my area in the mid-1970s.
Again, wishing you all the very best in your recovery.
With all best regards,
Dan.