Mouseproofing - better get it right!

Heard a curious story from a customer earlier today. We had attended their property (customer is the landlord, property is rented out to tenants) back in the autumn of last year to fill some holes where mice were getting in. This our handyman did, using our standard method of filling with steel wool and covering with filler and / or expanding foam (the mice eat through filler alone, but have not yet evolved steel-munching teeth). Filling the holes is the easy bit, the hard bit is being sure that you've found every possible hole. Customer then got the boys from Rentokil in to lay poison for any mice still in the house. This seemed to do the trick and the infestation disappeared.

Then the letting agent managing the property gets sent a dead mouse in the post, disguised as a Christmas present, from the tenants. Yikes. Seems a bit excessive, to say the least. Especially as another pest control firm checked after Christmas and could find no evidence of recent mice activity, so presumably the dead mouse was just killed by the poison Rentokil had laid down which is, obviously, the whole point of laying the poison. Finding dead mice in that context is a good thing, better than having live ones still running around.

To cap it all the tenants (who have now left, I understand) were Italian - talk about conforming to stereotypes, sending dead animals to your perceived enemies. Letting agent has, apparently, asked the police to look into the matter. Quite right too.

Understandably, the customer has asked us to come in again to fill some more holes which the second pest control company found, really does want to be sure that no re-infestation happens. What I don't really understand, though, is why Rentokil don't offer to fill the holes themselves? Seems like an obvious extra service to offer. I mean, we are happy to do it, but it does make it all more hassle-ful for the customer having to get two separate companies in. Hmmm, maybe I've got this the wrong way round. Maybe we should do the pest control bit? Mental note to find out what that involves (suspect lots of bureaucratic licensing to use poisons, etc., but perhaps not).