Good afternoon and welcome to the forum markp.
You certainly have some issues here that need resolving and I would certainly agree that using any remaining credit to "tide you over" so to speak will only add to your problems.
The house issue first. As any asset is only worth what people will pay for it then as it stands it is only worth £300k. However, from your perspective I quite understand that that figure is nowhere near what you would ideally want for it. Is it possible, therefore, to let it out to cover the mortgage payment, or at least as much of it as you can, until the market recovers, or alternatively going back to live there full time yourself? You also mention that you will have arrears from 1st jan. Presumably this is because ypu have so many other outgoings, i.e debts? If that is so, then you must divert enough money to pay the mortgage BEFORE you pay any other debt repayments.
Because there are a few imponderables in your situation, I would suggest that you speak to a professional directly as soon as you can. You may wish to visit
www.iva.com to have a look round there at the reviews etc. Take time to speak to 2 or 3 providers and make sure you know what ALL your options are before you make your next move. There will be a solution(s) for you, but you need to know the pros and cons for all the solutions, as they apply to your situation, so that you can make your own informed decision.
Regards.