We have a double story townhouse next to our house and their whole family has a shower without the blinds down. We see all there family naked every night.
We want it to stop because it’s awkward and we have children.
I have left them 2 letters in their letter box and they still don’t shut the blinds.
I can’t block out the view since they are a double story close to the fence.
What can I do? Can I speak to the council/police?
NEVER talk to neighbours about problems. They either listen and change, don't listen and continue, or turn crazy and do a lot worse. You never know which result you'll get, but you have two chances out of three of getting a negative one, and three chances out of three of being blamed when something happens to them/their house (they'll think you're "taking revenge").
So you say nothing, try to ignore it (to check whether you're just being a Karen), then deal with it quietly/covertly. "Dealing with it" depends on each situation but choose something they can't be certain about because clues lead elsewhere.
Random examples:
Their cat/dog keeps coming into your yard dropping landmines. Say nothing. Get a cardboard box from Bunnings, keep it in the garage/laundry, quietly catch it, put in the box, into the car, take to the pound. Tell them it wandered into your yard and you have no idea who it belongs to. Better still take it to a relative 20km away (with a different surname in case neighbour gets your mail one day by accident) and have them do it. If you do it, don't give a name, address, phone number, or make up fake ones. And NEVER say you live next door. i.e. Think beforehand. If they want it back they'll get sick of paying fees, will work out how it's escaping, and fix it. If they don't care about it, they won't pay, it gets a needle, and good riddance.
Frequent loud music. When it happens and you see them, give a quick smile, thumbs up and/or nod to the beat and/or say something like, "Metallica, yeah?" Put up with it that day. Next time leave home for a few hours. Try to ensure they see you leave. e.g. By stopping in the middle of the street while you/your partner/kids go back inside to get something, tooting the horn to come back or hurry up, etc. Some noise so the neighbours come to the window to notice you're going out. If other cars honk and swerve around you, even better. An hour or two after leaving and at least an hour before going home, phone the police with a noise complaint. You're not home so in their mind it can't be you who complained. Give the address on the other side just in case police open their big mouth. Mrs Feral says to Mr Feral: "They went out 2 hours ago and their car still isn't back. So it must be the @#$%^# on the other side." Do it every time the music starts. Have a supply of popcorn ready as their war on everyone else in the street begins.
See-through window with weird frosted glass that turns see-through? Wait til you see a dead bird, take it home in a plastic bag, while they're out smash their window with something like a nail in the hole you drilled in the end of a broom handle. Drop the bird over the fence. Birds fly into windows/walls all the time. They'll replace the window, hopefully use different glass this time. You could do less as some have suggested, like spray something on it, but they'll only clean it off and will now know a PERSON is involved rather than kamikazee wildlife. Better they pay $20 for new glass instead of you moving house because they turn psycho.
It's too late now but plausible deniability is king. Of course you could "go on holiday" to combine part of example 2 with example 3, to reset your plausible deniability quota. i.e. Even though you've already spoken to them about it so would normally get the blame, because you "went on holiday" (no lights or TV on for a night or two) it must have been the bird.