I hope the firm that you are speaking to can answer the questions that you have, Dakota. Were they recommended to you by someone?
Although you say there may be £15000 or more equity in the property, in reality creditors are happy to allow a reduction on this figure to account for the fact that the equity figure on paper is not actually the same as what could be achieved practically. A good insolvency practitioner will be able to get an agreement with creditors with this taken into consideration and you may well find that a Trust deed is much more realistic for you than you might think.
There is no reason at all to fear being suddenly asked to pay over equity that you cannot afford, as the equity should be exactly quantified and a suitable arrangement agreed before you sign up to anything. If the equity is higher than you can manage to pay off by extending the term by a short period then you would just not go ahead.