Banks have an option within their systems to let you draw against uncleared cheques - it is allowed only to preferred customers.
One issue here is that if the cheque was drawn on an Irish bank, then it is reasonable to assume after 5 business days that the cheque had been fully cleared - and regardless of your status with the bank, you would have been considered as the owner of cleared funds after that time. In this case, it seems that Poppy11 was informed of the problem "a few weeks later". This is outside the normal clearing cycle and you are entitled to a reasonable explanation as to why this did not happen.
Poppy, Can you confirm that the delay between lodgment and noticifation of the problem was significantly more than 5 business days? and that the cheque was Irish?
If you had earlier notification of the problem, would it have helped you to mitigate the loss?
If the answer to both is yes, then you should make a complaint to your bank, and if no satisfaction, then go further to the Financial Ombudsman, on the basis of undue delay in clearing.