Thanks all for the documents tips, I think different things work for different people but in the end I got 5 files of stuff down to:
-one folder of current bills (it's a document folder with different sections so labelled for Gas & Electricity, Water, Council Tax, TV Licence, Car Insurance and Misc)
-one folder of all product manuals and receipts for big items relating to the house
-one lever arch folder with dividers for everything else. I have 9 categories: Health/Medical, ID docs (birth/marriage certs, driving licence, passport copies etc), Payslips and work docs, Pension docs, Tax docs, Mortgage, Qualification certificates, Finance & Misc
I also did a charity shop run and got rid of 3 hats, one tote bag, 2 black bin bags of clothes, 2 pairs of curtains, an unused mug, some flower hair clips, 2 hanging shoe racks, 3 books and 3 scarves. Haven't been counting this year but have got rid of a lot of stuff so far including 16 old photo albums and countless old photos as well as old scrap books and more sentimental items that were just hidden away. We are lucky to have a lot of storage in our house but I don't want to fall into the trap of filling it with stuff for the sake of it so having a big blitz now and it's so nice that everything has a place and is easily accessible but still more to do!