I hope I can help.
I will need further details.
What do you want to take legal action in respect of exactly?
What is your loss, the rent income? For what period did you not receive rent?
If you can provide more details I will try to help.
You have 6 years within which to bring a claim for breach of contract so you can claim the 4800 loss from 2013.
You can of course claim recent losses.
You do this via the small claims court. It is fairly simple, you do it online at moneyclaimonline.com
You can try to claim your incidental expenses of flights, hotel and loss of income but this may be too remote to recover. The court will determine whether you can recover those incidental losses.
I think you need to formally write and send the letter by recorded delivery, with a copy by email.
You may want to consider giving notice in this letter to terminate the agreement (you will need to check the agreement for the conditions relating to notice), state that keys are to be handed over to you nominated person on a particular date (end of notice period and if they fail to do so you will change locks and seek to recover costs from them), make arrangement for any tenant deposit to be transferred and to be notified of the tenancy deposit scheme details in which the deposit is registered.
In a formal letter you should set out the rent which is due, give 21 days for payment and state failure to pay will result in you making a claim in the small claims court, not only for unpaid rent but incidental costs and expenses incurred from flights, hotel etc when you had to return to resolve problems with them, plus interest at the court rate of 8% on the unpaid rent plus fee to change locks plus the court fee. It could get expensive for them if they refuse to discuss and communicate.
You cannot make them communicate with you but if they fail to do so you can go to court to recover sums due.
You mentioned you had email correspondence where the agent alleged employee fraud. You could refer that to the police for investigation and mention in your letter if you do/will do so.
Any further questions or queries? Happy to help further.
Please can I ask you to accept /positive rate my assistance so that I can get credit for helping you.
You can still claim under money claim online.
The tenant should sue the agent for the deposit. If the tenant sues you you will bring the agent into the proceedings via counterclaim.