The only food they can eat is catfood, which yesterday I put out in the garden for that reason, and in the mouse traps. I hear a little plastic clink, which means there’s a mouse in the trap, and later on, in the evening, I see another one scurrying around looking for food.
The real answer to this is to hack through my ex-neighbour’s vacant vegetable garden bramble jungle to inspect the rear walls of my house. The answer must lie there.
Ours come in under the sink - almost impossible to seal pipes coming into house. They can get through such small gaps. That’s when they are not strolling in through an open door.
Exactly where ours came in, last time we had them.
This thing about why do they come in towards summer time, they don’t hibernate do they, was a question I posed at the time. Not inundated at the moment, but I have noticed a quick movement out of the corner of my eye now and then.
Expanding foam is excellent for sealing between pipes and the walls they pass through…
They will eventually eat through it though
Yup, ours do. 
Or use steel wool.
This may well be the mice entry point. When we bought our latest home two years ago we discovered mice frequently invited themselves in.
As new owners, we were finally able to trot around to the neighbours and request to view or rear façade from their garden. What a horror! No wonder our seller, the village doctor no less, had not granted our prior requests to view the rear.
All the plumbing pipework for 4 new shower rooms and multiple unexplained, some surprisingly large, with no covers or finishing. I was really surprised that the neighbour was so friendly and accepting. Especially considering all the works had been carried out by our seller during their absence in holiday. Needless to say, we had our mason in within the fortnight and the entire wall re rendered and holes filled or covered with metal air vents, depending on what they might be for.
The results for our little mice friends’ access was immediate and we see them no more. Bit of a pity as I was giving them names…
I think so. The old neglected vegetable garden behind my house is a haven for field mice I’d have thought. My front garden and the grass chemin would be suicide alley for them.
I have one outlet in the rear wall, from the shower room at about 3 metres up, but mice are good climbers, and I can just see, on tiptoes, that ivy is more than halfway up the gable end of my house.
But before I can do anything I have to penetrate about 10 metres of what is a bramble forest - this is where the gate used to be.
Bramble-proof gloves and all necessary garden tools are being readied for the attack….not forgetting tweezers for the ticks!
Oh it’s like The Secret Garden. That’s not a bramble. That’s a beautiful rose! 
That’s just the pretty entrance - bramble lurks beyond. I shan’t hurt the roses…just prune them a bit…
We’ve been away a few weeks and have just got back to the house and it seems that we have a kestrel nesting in our wall. Not the best picture but they’re really quite fast, and this was it applying engine braking to get into the hole in the wall.
Cercopsis - froghopper according to Google Images.
Oh no they lay spittle bugs which I’ve had before. I wonder how I can get them to go elsewhere?
Ask them?
Classic 
It’s a human hand, oh, and btw there appears to be a Froghopper on a leaf nearby too. 
@SuePJ 's advice is good, I’m told they understand Australian perfectly. 
I think they’re the things we have loads of but they always seem to be in pairs, joined at the rear end… Must watch more carefully as logic says they must have problems getting about like that 
Small bucket of warm soapy water, pick them off and drop into the water, repeat as many times as necessary. 
