should I use 'without prejudice' in the letter?

How would I file a case against them? Could I do it myself? or would I have to go to a solicitor to prepare it for me? Within the letter do I have to give a figure as to how much I would like to be reimbursed? I take it I wouldn't have to give a breakdown in the initial letter to say how I got to the figure as they didnt send me a breakdown to say how the hell we owed their client £40k odd!!!

Bookworm is right, I called Shoosmiths on the phone but saw a local solicitor to prepare a defence. I asked for confirmation in writing they took over a week to send a letter out, the date I finally received it was about 2 days before the date that the defense had to be into the court by. Would it be Shoosmiths I'd ask to reimburse me or would it be Natwest that would actually pay out? Thanks for your help by the way!

Hi This is my first post on this forum, I'm hoping someone may be able to help me out a little... Here goes.. I'll try to summarise! My mother and father were involved in a bankruptcy many years ago. £50k paid off all the outstanding debts (they thought) NatWest (one of the creditors) still chasing around £6k Parents receive a letter from Shoosmiths (representing Natwest) asking for £40k - parents know nothing about this and get really worried, taking time off work, making me take time off. Then a CCJ to be heard at Northampton Bulk Centre. Tried seeking free legal advice as they couldnt afford to pay for it. I took time off work, saw a solicitor, called shoosmiths, started preparing a defence, shoosmiths didnt want to talk. Then two weeks later they write back saying we made a mistake. Can I complain/ gain compensation for the loss of earnings and the money paid out to the solicitor?