Assuming you have kids and are a 3-5 person household, including children, I'd do something like the below:
Chicken and not turkey - mostly because turkey always disappoints - with, frozen carrots, homemade potatoes, Yorkshire pudding, usually creamed spinach (super cheap to make and very filling) and runner beans. That would be about £20, I think. It means more prep on the day but it's worth it.
Buy things like a big desert or cake when it's marked down in the store an freeze it (most de-frost very well even 2-3 months later)
Don't do salad the next day, salad prices sky-rocket over Christmas (because everyone seems to want it). Instead, I'd do chicken wraps or something to use up leftovers.
Instead of buying the nibbles you might have, try and make them yourself! You can usually make 3-4 times as many but at 1/8 of the price. It's also a good way of entertaining children the day before and lots of them also reuse the same ingredients. Also you'll likely have the 'core' ingredients (like flour) already!
Adults don't do gifts for each other
Children get one 'big' present (set a limit on whatever the budget can be) and no stocking but instead lots of little presents (£5-10) each. I find stocking gifts are usually just crap anyway unless you're super rich
Buy the smaller gifts long before christmas and hide them away.
Don't bother with big events (I know kids love Christmas lights, but so often they are just overpriced) and instead do things like home movie nights with Christmas music, big bags of popcorn (the microwavable ones are super cheap, not the ready popped ones).
Check out charity shops for cheaper Christmas decorations.
Be careful of places like Amazon (last Christmas one of the presents I got DD1 was £40 more expensive on Amazon than it was in John Lewis) and shop around.
Be clear to extended family (siblings/parents) that you're prioritising your children's Christmas memories this year because of the financial situation (assuming you have kids). A good family member will 100% understand why you cannot give them a new sweater.
Don't be fooled by 'homemade' presents - I tried candles last year. Cost me a fortune to buy everything I needed and tbh I could have got 4 Yankee Candles (which are insanely expensive IMO) for the price of the 40 tea lights I churned out. Also the Yankee ones probably wouldn't have smelt like dead flowers...