It depends on the nature of your business. Ideally, you will have a credit application form which confirms that the debtor agreed to abide by your terms and conditions. You may have proof of delivery forms showing the goods were delivered. All of this documentation is extremely relevant and will be used to prove your claim. What one Judge thinks is reasonable will invariably differ from another Judge.
Some industries are better than others.
In the late 1980's building companies who were in the grips of the recession frequently failed to respond to anything at all as so many of them were going bust. Having said that, a Solicitor's letter does indicate to your debtor that you are serious about pursuing them. Quite often credit control departments send three or four chasing letters and say they are going to instruct Solicitors and don't and even worse in our view, say they are going to issue their own proceedings, get as far as drafting a Summons, sending a copy and then do not issue. You must tell us. Whilst we will never issue proceedings until we obtain your instructions, we do require to be notified that you have been paid as this will stop us sending chasing letters to your debtor, who might not appreciate receiving threatening letters once the debt has been paid.