First of all thank you for your reply.
At the moment they have not mentioned any court action. We are only still receiving the letters from the debt collectors. The latest correspondence we received from the HR ( a month ago) is that they have concluded their investigation and that they expect the payment of £525 (approximate as I do not have the paperwork with me at the moment).
They also stated that: "The post to which you were appointed is graded at BR6, points 17 to 21; you started on point 20 and the full time equivalent for this was £21153. You were employed to work 35 hours per week for 39 weeks per year so the pro rata salary was £17616".
Another thing they mentioned was:
"I have clarified the appointment details with your Manager and asked him what salary was offered and as far as he’s aware it would have been the pro rata salary that was confirmed to you and stated in the contract your received."
The last quote is quite interesting as my husband only received his contract 2 weeks after his resignation. As my husband was reluctant to hand in his notice at his permanent job (where he worked for 5 years and walked to work for 30min) without a written job offer (for a new job where he would have to commute for 1.5hrs), the manager sent him an email stating:
Please accept this email as a contract of employment.
The details agreed are as follows;
One week placement with PPA at X from 19th to 23rd of October 2015 at agreed daily rate
One year FT fixed contract with potential of permanent FT contract to follow from 26th Oct 2015
Rate of pay £21k
Main correspondences we have are the email exchanges between my husband and his manager. He never received his contract or any such paperwork describing the conditions of employment. Nothing was ever signed. We just want the harassment to stop and to resolve the issue once and for all. If we are in the right, what can we put in the letter to the HR? Or should we just wait till they threaten us with court action?
Basically the issue is that the manager said he would be paid till the end of the month as he was, but now he changed his story and they want half of the month's salary back. We do not have that money anymore as we have used it in the purchase of our property. Do we ignore the issue or confront them with a stern letter?