Blimey, Ouch poor Gaz!!!!
I would look at WHY they are taking this interest in you?
Firstly it could be a junior manager poorly interpreting the rules on sick leave. They have failed to exercise reasonable application to your circunstances.
Organisations have policies and procedures for good reason. A Council will be no different. If they do not follow them or apply them arbitarily then they can be onto a hiding to nothing.
There seem to be several aspects to your current predicament.
1) Your RTA resulting in your time away.
2) Your relationship with your employers.
3) Application of policies and procedures.
I would speak with a Union Official but NOT one of those reps who is merely using union work to expand their CV. Maybe you can speak with the Union's legal help line who will give advice regarding your employment relationship - what is happening to you does it amount to harassment, bullying or breach of contract and advise you on the other aspect which is your RTA and resultant injuries which would be a PI claim against the local authority.
It may be that behind the scenes some one has thought, this is going to be REALLY embarrassing IF our employee decides to sue us over his RTA which incidentally you can do whilst still employed but which could become tricky though depending on your role and responsibilties at the Council. Do you work in the department that has responsibilty for highways? Can you see the conflict I am alluding to? I suspect your employer may be anxious should you choose to bring an action against them as a road user who has been injured on a road they have liability for. Being knocked out, hospitalised and having two weeks off work and then perhaps being on less demanding work activities when you return, might just be spooking them, given they may be the organisation with liability for the road and your employer.
If you feel your treatment is without justification or without foundation then seek a written explanation from managers. If you are not satisfied with this then approach HR and commence a grievance procedure.
To me and everyone else on here it would seem the Council are setting themselves up for a big fall. But unless you stick up for yourself your life will be made miserable and they will force you out. If the matters you write about cannot be resolved sensibly and reasonably to your satisfaction then I would have thought that any action you brought against them through exerting your employment rights or personal injury would be SUBSTANTIAL.
I would suggest you seek specialist employment and PI advice from ideally an employment lawyer and PI solicitor respectively. Maybe your Union or the CTC (Russell Jones Walker) could assist? Watch out for any conflicts of interests though as large firms of solicitors such RJW can work for both employer and employee. You need fully independent advice so ask the people who you seek advice from whether they have or are representing your employer? AFAIK RJW represents union members was well as CTC members. RJW used to provide legal advice to members of the IPMS Union.
Make records of all conversations and meetings. Try to get witnesses or some one independent to attend with you at any meetings which you are entitled to. Try to stall impromtu meetings by saying your chosen companion is unavailable. You should at least have 24 hrs notice of a formal meeting with management and be given an opportunity to arrange for a companion of your choice to attend with you. Also any informal chats with management which you feel could be material to your circumstances try to get in writing. You could say "Any chance you could email that to me?" Then print the emails off in triplicate.
Try to establish whether managers have deviated from laid down procedures at any point. Some one mentioned back to work interviews and occupation health. I would have thought involvement of OH was obligatory where some one had been hospitalised becoming unconscious because of an RTA, surely? Your employer has a duty of care toward you this includes a situation where you have returned to work following serious road accident of which they are clearly aware. They have to make adequete allowance and cannot just side line you. Occupational health should be able to identify what you are capable of and any assistance you need to carry out your role and recommend any allowances that should be made by managers. As I say if they have not done this then they are on a hiding to nothing.
What a shocking turn in attitude from an organisation that appeared to have recognised your achievements so highly. They will find it hard to rebutt this.
Bottom line is do you wish to continue working for them? If so seek amicable resolution keeping things very cordial giving them a very large benefit of the doubt, maybe some one has exceeded their authority or has arbitarily taken exception to you; if you don't want to work for them then get dirty and sue the ass off them.
Good luck.
Ps. I wouldn't involve the press at this time as this may be viewed by your employer and tribunal as breaking the relationship of mutal trust and confidence which is implicit or expressly stated in employment contracts between employers and employees. Maybe after it is all over if you still remain dissatisfied you can call the local rag. I think employment tribunals are public anyway. Not sure.
so the knee is getting better, cant wait to get a hold of my 
so the knee is getting better, cant wait to get a hold of my 
