Last year we had a "prepping for a frugal Autumn / Winter" chat. I'm going to try and outline some of the points I remembered. It will help me and hopefully a couple of others too: it's a good time to check eBay for some Winter stuff!
Hats, gloves, scarves and thermals
Winter boots / wellies
A decent Winter coat
Puddlesuits
Slow cooker! (Stews, chilli, soup, spag bol, curries and casseroles!)
Stock up on hot chocolate, tinned soup, custard and other tinned foods
Pick blackberries for crumble
Fleece line curtains
Make your own draught excluders from old trousers, leggings or tights
Have a curtain over single glazed or draughty front doors
Add fleece blanket underneath bed sheet.
Have an extra blanket for on top of duvet
Brushed cotton bedding
Fleece blanket for the sofa
Thick socks, tights and leggings
Thick jumpers / fleeces
Rugs
Slippers and dressing gowns
Brushed cotton PJs
Hot water bottles or microwavable bean bag things
Stock up on strepsils, paracetamol, ibuprofen, cough syrup.
Not sure if it works but Wicks & Homebase sell "seasonal double glazing window film"
Lakeland's heated airer is less than 6p per hour to run.
Turn down water temp on the boiler.
And replace all your bulbs for LED bulbs!
I've obviously tried to type this out as quickly as possible. I know it's only August but some of the stuff above may be cheaper to buy now than waiting until it's in season. And some of it could be going cheaply on eBay.