Again thank you for all your replies. It was especially interesting to read your story drowning-mummy. Hearing from someone who is going through this at the same time - someone who still finds time to type a response - it means a lot. I do hope everything works out for you.
I have to say the more I think about it the more I think I will take this option. I do worry about calling people though, no matter how nice they are, because I have nothing to offer in return. I've looked at some of the sites linked from here and thought about picking up the phone - but somehow I'd feel I was cheating people using the services. These people have to make a living to - and all I could do is take up their time and effort with no realistic chance of being able to take up their professional services. It seems wrong.
I guess the next stage is to take the step I have dreaded for the last few years - finding out what I actually owe. At some point this week I have to take the excellant advice above and query Experian to find out the exact details. I must confess when that letter arrives I don't know how I'll react. But it has to happen at some point.
So - courage in hands - time to start the process.