I would explain to the landlord/agent that if no previous certs are available, then I would prefer to start working my way through them now irrespective of when they say they were last done (state company policy)
It may (short term) save them a couple of quid now, but at least it shows you are responsible/ conscientious and should put you in good stead with them . Also, explaining that any minor problems that are encountered now can be rectified before they could possibly turn into disasters, therfore saving them money
Obviously all the above is speculative as I know nothing of your situation (reputation of landlord/agent or ammount of properties)