I don't live in the UK but I read Saturday March 11th is their second 'Clear Your Clutter Day'. The event was founded just last year, in 2016. However, it seems the idea of a 'Clear Your Clutter Day' has been around for a few years. I saw an item (dated January 2016) about the '10th Annual Clear your Clutter Day' in Austin in the USA. That such a day exists is surely a sign of the times.
The idea behind Clear Your Clutter Day is for people to sort through the house and decide what they don't need and don't want. They then donate, sell, swap, recycle or if it's broken beyond repair, dump the items.
Today the internet is full of blogs written by individuals who have tackled clutter in their lives. They tell of a sense of freedom once they had parted with the clutter that had been weighing them down. There are plenty of books and articles about the benefits of decluttering. It is easy to find tips of how to approach a decluttering project. Dealing With The Problem Of Clutter Part 2
If all this advice doesn't help, it is possible to pay someone to come into your house to help declutter and then organise the things you are left with.
A person who has a hoarding, rather than a clutter, problem may benefit from talking to a counsellor or therapist (a GP can make an appropriate referral) about the issues behind their compulsion to hoard.
On some web pages about Clear Your Clutter Day or general decluttering I noticed advertisements for storage boxes and filing systems to help people organise the items they are keeping. Sometimes proper storage systems are useful but at other times perhaps a person will find they already have enough places to store their possessions once the task of decluttering has been done.
One doesn't want to get all excited about buying lots of pretty shiny tubs with lids only to find some of them aren't needed. If they are surplus, even if they are new, they are clutter. That's ironic.
There are other adverts on some decluttering sites which encourage readers to buy a stack of inexpensive jewellery or clothing. Sometimes shipping is free, but only if you spend above a certain amount. So while people are reading decluttering tips they are being tempted to start accumulating things they probably don't need all over again. Consumerism perpetuates the problem of clutter.
I expect in the future more places will declare a 'Clear Your Clutter Day' to encourage people to cut down on the amount of stuff they hold onto.