For a boat that size, you're looking at some where on the south coast between Fareham and Southampton for ease of access - A3 or A31 someone with knowledge of marinas will be along in a moment.
You say you've not done boating before so I assume at some point you'll be taking tuition. If the...
Google marine surveyors for your chosen location. Insurers have taken to asking for surveys for new policies and then every ten years. Mine was surveyed while I lived aboard by a UK qualified surveyor.
As someone else has said, your best course of action would be small claims court. If you don't have the required information to submit an online claim, it's unlikely you have enough information for any other (legal) remedy.
Are you talking about general fire, or engine fire.
We had specialist kit in our engine bay, but used to buy Lidl special offers at £10 as they fitted the holders on the boat. Lasted several years before gauge went red. Plus fire blanket in galley.
When we bought our 10 year old boat we drew up a list a bit like SC35s, but no matter how many jobs we did, the list got longer. So we abandoned it and took the approach "is the boat sinking, is it a safety issue or is it annoying the hell out of me" to decide on jobs to do.
From my experiences, it is the residency of the owner - insurance for boats and cars is the same.
Since you have dual UK nationality, can you not come up with a UK address which might get round it.
I'm UK resident.
My boat insurance was registered to my UK address (insurers knew boat was in...
1. Toilet use briefing.
2. Location of fire extinguishers and escape hatches.
3. Written instruction by the helm on radio use, call sign and how to send Mayday or Pan Pan.
4. Don't go down polished teak steps in socks.
I used Bishop Skinner, and provided a list of all items I wanted covered, with values. Everything was covered (except money) at an additional cost. Can't remember how much - 20 years ago when insurance started.