I'm surprised your credit card coy are not looking at your claim, for two reasons: firstly, if an FCO warning was in place against travel to the area art the time of your booking, that should be sufficient grounds for a claim on its own, simply because you could not get there and so you were not able to receive what you paid for. Secondly, if TtoT have liquidated, and I'm not sure that's absolutely the case, since their website is still extant and it states it "is not trading at the moment", that means they are in no position to offer a solution, and to me, that is even stronger grounds for your CC coy to honour a claim.
Unfortunately, I am not a professional in this field, so I can only offer advice on my personal experience. Here's a couple of things you could try: a lot of insurance outfits (especially online outfits) are subsidiaries of major coys, many of them foreign, whose names might not even suggest they have any connection to insurance. I would contact the Financial Obbudsman and get their advice. They will have access to records that we don't and will be able tell you advise you. Although the subsidiary might have been conveniently liquidated, the parent coy might be liable for claims? Also, a good source of advise is the Citizens Advice service. If you get in touch with them, ask to speak to someone who has specialist knowledge re credit cards and insurance.
I'm really surprised your CC coy are not looking at your claim. Have you tried contacting the relevant dept, usually the fraud department, and talk to one of their claims people? My coy was very helpful and supportive. If by any chance you do get them to look at your claim, and it is successful, you will have to keep hold of the money for 45 days after it has been awarded as the coy you have claimed against can request to reverse the chargeback. If TtoT have gone bust, they'll hardly be in a position to contest the chargeback. Remember as well, the chargeback is conducted bank to bank, so if TtoT is bust, that should not make any difference as it is their bank that hands back the cash.
I'm so sorry I can't be of any further help and I would suggest you keep hacking away. I started trying to recoup my losses in April and it took me until November to get a result. Ironically, the only company I had no trouble getting a full refund from was Ryanair for my outbound flights. Getting a refund from Bast*Rd Airways was as tough as you'd suspect. I kept a spreadsheet with dates, contact details and notes of everybody I dealt with during my claim, a good ploy, since you will be phoning, writing and emailing all over the place and its a good thing to accurate dates and records.
Good luck