[Closed] Dare I ask?.. Advice please on road traffic fracas

I appreciate this isn't the best place in the world to ask but I figure someone out there may have a golden gem of advice and/or experience.

Driving to work earlier in the week I was nearly driven off the road twice by a big Mercedes 4x4 thing. Genuinely, his driving was utterly appalling at best. Threatening/bullying and dangerous.
Between first and second swipe/interchange we exchanged pleasantries and gestures through the closed windows of our cars, then at roundabout junction Merc driver kept flashing his lights and gesticulating. I pulled over, partially blocking Merc, and got out of car to find out what the guys beef was (2 people in Merc) - as I approached driver also got out of car and started shouting - I got close to him the next thing I know we have grabbed hold of each other - he's shouting 'I smash you!' (he had strong foreign accent) etc, whilst passenger is screaming blue murder - I thought I heard 'cut him' or 'hit him' coming from car so im on full alert - im shouting 'get your hands off, get back in your car!'
Other blue words were obviously shouted.

Next thing, he stoops down and attempts to lift my leg in order to unbalance me and get me on the ground. I continue to tell him to get off, approx 20-30 seconds pass of this weird wrestling stalemate and at this point I have a weird lucid moment and begin thinking 'wow - this escalated quickly' and 'I really don't want to be here right now'.

I refrain from throwing a single punch, im lucid enough to realise that a)it could get much nastier b)could be taken further..which I dont want.
I'm also really close to my office..

Next thing, guy has managed to throw my balance and im on the ground with him on top - im pushing him yelling to get off me - female passenger has now exited car and run around to start attempting punching my face - I use left hand to hold her back/block her - right hand to hold driver back.

Driver of a van in traffic queue now runs over telling driver (and me I assume?) to calm down, and pulls him off me.
I get up, attempt to tuck my shirt in, and start walking away - he continues to shout threats about smashing my face in etc etc.
I get in car and head straight to office.

Obviously during all of this im extremely shocked, adrenaline has kicked in, and aspects of the incident become hazy. I just remember feeling really embarrassed and wanting to get away.
Im not one for taking things further in terms of solicitors etc (unless very serious incident). I guess im brought up a bit old school in terms of, if there's a problem, have it out with someone, then call it a day. Granted. Perhaps not best practice.
I have a sore thumb/wrist, a grazed knee, a bruise on my throat and a few buttons lost on shirt.

I didnt report the incident. I appreciate this may have been a mistake. However, my general feeling is an overwhelming sense of shame and embarrassment at being involved in such an event. I've certainly been doing a lot of inward reflective thinking since.

So last night I get home to find a letter from local Police force asking to confirm my details as my car has contravened Section 170 of Road Traffic Act 1988 (leaving scene of accident).

Obviously, this worries me as all I can conclude is either
a) local CCTV thinks its witnessed a hit and run event
b) Merc driver has reported incident
c) witness has reported incident

Letter is from Central Ticket & Summons Unit - Road Collision Dept. There is plenty of cctv coverage in local area.
Is this likely a Police attempt at pre-interview confirmation of personal details? or more likely an automatic/procedural letter to an event caught on CCTV?

I can confirm that at not point whatsoever was contact made by/to either vehicle.
Also, neither driver or myself physically threw a punch.
I did approach the driver, I recall hands being raised, possibly me finger pointing, I remember trying to push him back towards his open door - its very hazy.

What next?
I have 28 days to respond to letter, which is tricky, as effectively its asking me to confirm presence at an 'accident/collision' (which there wasn't).

Citizens Advice have recommended possibly seeking legal advice as not really their area of expertise. Im thinking of contacting a few 'free consultation' road traffic specialist solicitors.

In my mind the incident is probably a 6 of one/half dozen the other event. I could possibly argue driver used excessive force on me, im sure hes likely to argue that I threatened/used force first. He also has his wife (and possibly van driver?) as a witness.

Is this something that likely to be taken further?
Naturally im very worried about implications, and I certainly don't have any budget to fund any sort of defence/counter-claim. I have zero previous, no offences, no convictions.
I can imagine that sorting out events like this is a nightmare as its pure he said/she said.

Would really appreciate some sound advice. My anxiety levels are through the roof. Thank you.