Advice needed re Cavity wall insulation

Maintenance

I need some advice regarding the cavity wall insulation at one of my properties.
I had arranged for the loft to be insulated, which was done as arranged, however the next time I visited my property I noticed drill holes in the exterior walls and the air bricks blocked up with silicon sealant. I asked the tenants about it and they said that it was done at the same time as the loft insulation. I was pleased - the house fully insulated at no cost to me!
When our tenants left we did the usual repair and redecoration and when we removed the vent covers in the kitchen I noticed that the insulation in the cavity only reached half way up the wall. I contacted the company I had arranged to do the loft insulation and amazingly they totally denied that they had also done the cavities!
So, I have two problems, firstly - I can't get the cavity insulation brought up to standard. Secondly, and more importantly - the air bricks have been completely blocked with silicon sealant (presumably to stop the cavity insulation leaking out).
Will this affect the ventilation of the underfloor areas? I may be mistaken but I've always believed that blocked airbricks lead to damp & rot in the joists.

Any advice will be much appreciated.

regards
FAZ