So much advice. Some good, some bad and some that doesn't apply on this planet

Why do people feel they can offer advice on a subject that they have no knowledge of?
Visit your local CAB. Most are very good at helping with this sort of thing. Phone them first and arrange an appointment. Tell them it is a debt matter. This way you get to see an expert in this area rather than a general helper.
Do exactly what they advise. But make sure that they do what they say they will and do so in a timely matter. The main criticism I've heard of CABs is that some can be slow off the mark.
Whatever you do, do not approach any of these companies that promise to assist in handling your debt.
With the agreement of your CAB advisor, try to make nominal payments every month.
If you consider the level of calls and letters constitutes harassment then write to them and say that. Once you complain of harassment and ask them to cease then they have to - by law. But it is always best to keep open a channel so, in the letter telling them to cease harassment, tell them to write to your CAB advisor and give their full details.
Keep copies of everything. Maintain a log of calls made, letters received/sent, visits to CAB, payments made.
Good luck.
p.s. get the CAB involved asp - before they pass the matter on to either their in-house debt recovery firm or an outside agency. This only complicates matters and adds considerably to the belief that the left doesn't know what the right is saying/doing.