So I've driven the Jimmer into a fence post, at speed... What next?

I think ir's too far gone.  Other Jimnys will live on from its spares, though.

Thanks again everyone. What's really paining me is that this is a VVT automatic with relatively low mileage. Finding something comparable to this with the ~£4k payout is just impossible. Even if I got them to push it to be more like £5k it's realistically not going to happen. I'd buy a new one if the money covered it but it just wont and then there's the logistics of me actually getting to a seller when my partner is working. 9-5 with the other car.

Really, really glum about it all. Only had her a bit over 6 months

It could be worse. I got loads of gear and mods in my car and it is not insurable here in Norway because of the prices. The extra gear and mods is not possible or too expencive to insure here in Norway.
Any cars with a pricetag under 10k is not economically to pay for the insurance here. why pay 1000£ insurance for a car that would give me max 6000£ in insurance pay out. Better to put that money in the bank or better investments.

It is insured from theft or fire or if someone else drives into me, but not insured from me.

If I where to crash it, it would be a total loss except for any salvegable parts..

Sounds like you should look for a donor and take it from there if you get to buy the wreck for a sensible price.

I think it’s probably dead. The way the door is opened at the front suggests that either the screen pillar or the door post has moved. 
That’s going to take it beyond bolt on repairs. I guess you could spend a day with a porta power and see where it gets back to, but I think it’s time to look for something new. 

Sorry to be the bearer of bad news! 
 

I just got off the phone with a friendly mechanic / panel beater at a local accident repair garage who did some welding work for me in the past. I sent him the same photos as in this thread and his outlook was basically "professional opinion 'give us the work' but personal opinion really sorry mate but it's better to just take the loss".

For all the reasons my head knows but my heart doesn't want to accept. I.e. it's a multi-panel repair, the A pillar could be misaligned, who knows if it's still tracking straight, maybe a brake line has ruptured, hell it could have actually been a catastrophic mechanical fault that sent me off the road in the first place so that'd maybe need repairing too... Then there's fixing the windscreen, replacing the headlight, even the fluid reservoirs. Then consider that it'll be forever a Cat S/N so resale value will be worse and insurance will be higher (well even higher considering I just claimed). Even the absolute best case of zero structural damage still sucks from a repair perspective.

So yeah, a dose of reality from a third party who was also quite clear in expressing his hatred for insurance companies (despite working with them every day) because of their propensity to screw people over. He also strongly advised contesting the valuation given the spec, condition and the fact it has had recent remedial and rust preventative work done on it (for which I have receipts). Lastly he anecdotally shared he had a write-off a few years ago where the initial value was £6.5k but because of his contesting it they eventually gave £10k - so basically just keep pushing and pushing giving all evidence possible.

I'm still absolutely gutted and sick thinking about it at all but looks like head will win over heart. I just need to get as much from the insurer as possible.

Don't forget that the Jimny is a body shell mounted on a chassis, unlike most cars these days that don't have a chassis, just the body shell and if the body shell gets an impact it writes the car off.

So the A-pillar and the rest of the body shell on your Jimny could be badly damaged, but the chassis might well be still straight and the shell un-bolts. It is a lot of work but if the engine, chassis and most of the drive train is fine it might still be worth it.