Look at the price per kilo on veg and fruit. We only buy strawberries in season when they are local and cheaper.
Eat less meat. (There is a reason some of us can magic chicken) (good for the environment too)
Turn off the shower while you soap up. (Not so great in winter)
Wash instead of bath or shower. (1970s habit) (bits and pits)
Wash clothes less often. Rewear if clean.
Cook with the cheapest veg as the main ingredient and add other veg more sparingly.
Make a shopping list and meal plan.
Ease back gradually if you can. It's easier to adjust. Live within your means, try to save for emergencies.
Wear layers. Wool is good. Try charity shops. Buy large socks that can fit over small socks. If you sit at home to work, a rug under the feet and slippers help.
One from student days: wear a hat to bed.
Look up jack Monroe recipes.
If you use spices get them from world foods aisle.
Beans on wholemeal toast is sufficient meal.
Turn off lights you don't need.
Claim your tax for working at home.