Ok so mid 40 year old guy here with a lot of experience on this!
Firstly...do not challenge the insurance company just yet. You need to have a plan of action regards exactly what grounds you are basing your complaint and also your wording etc. Be careful how you proceed. Don't screw it up for yourself as you actually only do get one shot at this.
First Google Policy Assist...they are very very good people. I'm not based mainland UK so they couldn't really actively help me but they literally sat on the phone with me for 2 hours giving me free advice and it was the only useful advice anybody could give me out of over 280 phone calls over 7 years.
Unlike the financial ombudsman who are actually about as much help as a chocolate teacup...the guys at policy assist can actually help.
They charge a fee as it's an actual service BUT they are pretty genuine....they were honest with me and said they wouldn't take my money as my one is complicated although innocent and they weren't confident enough they could be successful.
They can help you challenge cancellation and if your mainland UK...can help find you a policy.
I'm same as you...never had a clue it was even a thing....
I made an innocent mistake...we are literally talking paperwork and post here...literally nothing else. Nothing withheld, nothing purposefully undisclosed. And very genuinely nothing that I could ever have had control over.
Yet I was left in position where within 24 hrs of recieving an email, I was facing loosing my business. Eventually lost my family as after 2 years it was ruining us.
The worst was that nobody would actually give me details...stating data protection...I had to do a data request...it took 3 months to get info that allowed me to dig and find why my policy was voided.
In the first 6 months after my policy was voided, I spent £14000 on hire vehicles and was actively working from 6am until 10/11pm 6-6.5 days a week for approx 50% of my income to try and keep cogs in motion. I didn't eat much, I didn't buy anything...and I really do mean anything..for myself.
We were already coping with stresses 99% of average families with kids thankfully don't have to suffer.
A profoundly disabled daughter, a young teenage son suffering clinical psychosis.and attempting suicide, a long distance suddenly relocation due to the above, family home at other end of country in half renovated state due to being badly ripped off by a building squad and a Mom who was suffering PTSD.
Eventually I actually had to leave the country to enable me to insure and provide income for my family that was by then, no longer with.
I'm a normal, honest, crazy hard working guy with a clean licence, no accidents, no claims, no points, no convictions...and I'm uninsurable in the UK.
I've spent the past 2 years sleeping in back of my van when away working to ensure I can fund the kids and give their mum money for the half finished house which I intend to keep and repair, sell and eventually (they don't know this yet) just build them a home that they can have forever to be safe in. I intend to just rent for rest of my days when I have it all under control.
All of the above current circumstances are the direct consequence of an insurer voiding my policy over something utterly trivial and actually something that wasn't within my control to inform them off as I did not know. Without allowing me the opportunity to defend myself.
This took place 2017. I'm still suffering the consequences.
Currently stuck with a completely unsuitable vehicle that's now knackered and costing me £4000 average per year on repairs and 1400 tax (yes that's right...1400)due to being stuck with 1 insurer who will only insure me on this vehicle.
Still uninsurable in UK.
At one point during all of this I became so low I had a period where I had an overwhelming urge to end things. But thankfully I was able to pull myself together as became self aware enough to spot the red flags in my thoughts. Never thought I'd be "that" guy.
Desperate to come home and be close to my kids.
Desperate to even come home to be around people.
I've recently been taking steps to prepare something (exactly what...I still don't know) to make noise about this law/policy in general as it's almost cartel like in how it's set up, adopted and put into action.
So yes...rant over...google policy assist. Good people...straight, honest and knowledgeable all about this...every little detail.