Result!!!
Some may remember that my credit card company repaid my deposit payment (£307.50) to lowcostholidays for hotel accommodation. I was then pursuing them for the final payment (£432.02) made on debit card. I said that I had financial advice that they were liable even for the part of the payment not paid via them and would go to the Financial Ombudsman if they didn't cough up. I looked online at my current account a few minutes ago - and, hey!, in the "Money In" column there is £432.02 credit.
So for others on CBF who have problems with airlines or travel companies going bust, remember ... if part of your loss was paid by credit card then all of your loss is covered. Just be persistent.
[P.S. I can see that banks may complain that this is not fair. I have some sympathy with that view. But then credit card companies make a nice profit by us using their cards and, usually now, we have to pay a supplement for using the card. One of the reasons we are willing to pay the extra because it gives us more security for our spending. So my sympathy doesn't go very far].