Sorry to hear about this.
Firstly , you can make a written compliant via the internal complaint procedure of these letting agent company , for the inconveniences you had to face due to actions or inactions of these agents , and ask for compensation.
You can also report this agent to the Environmental health of your local council , professional regulatory body these agents are member of.
If the matter is not resolved by any of these options, then you can initiate compensation claim against your Landlord for your inconveniences . Before you start a court claim for compensation, you must send a formal 'letter before action' to your landlord and their letting agent. This letter must set out the detail of your claim.
You would need to file form N208 for claiming the amount.
Click below web link for the relevant form and guidance-