Mice in my water butt!

[inmysparetime]

I found a dead mouse in my water butt on Saturday and got DH to fish it out .
I did loads of watering to get rid of the manky mouse water, but checked the water level this morning only to find another floating mouse corpse. The only problem now is that the water is 3/4 down the water butt.
Would I be best filling up the water butt to raise the corpse to a level where DH can fish it out, then try to use up even more mouse water, or trying to empty the water out so he can tip up the water butt and scoop it out.
Also, any tips for preventing mice getting in? It already has a lid, I think they must be getting in through the drainpipe.
TBH, the whole thing is turning my stomach.

The mouse corpse is beginning to smell due to the heat, any advice would be very welcome MN.

Grill at the top of the drainpipe?
Eww to rotting mousewater, I'd want to drain the whole lot away! But in reality does it matter? After all, rainwater off a roof will be contaminated with bird droppings and any amount of mankiness /debris etc, and given the majority of areas in a HP ban it's a shame to waste the water! Scoop the corpse out and use up the remainder, then grill to stop any future drownings.

There is no way I'm dealing with the corpse, I'll get DH to do it not before dinner though I have an irrational fear that it will come alive again

sorry, but zombie mice invasion -

However, having read this, thread I am NOT going to look in our water butt, ever again!!

Mouse has been disposed of by DH, although the slovenly efficient bin men took only the bin bag out of the wheelie bin, and left the previous mouse corpse and a load of fox/cat faeces, and will not pick up the bin again until after the bank holidays. Bags I not opening that bin next week.