Kerosene - you describe exactly the situation that puzzles me, struggling to pay for a replacement boiler, having already spent your Christmas fund. I can see what you mean about feeling soothed by already having presents but, what I think I'd be feeling, especially if I really didn't have money for the boiler and was going to be cold or expensively indebted as a result, is annoyed with myself for spending money I didn't really have, spent on the assumption that I was richer than I actually am and having to face unpleasant or expensive consequences, when I could instead have scaled back the Christmas gifts.
I suppose if you're only buying a handful of £5-10 and one or two £20-30 gifts anyway, the difference you could make with fewer smaller ones wouldn't be much of a dent in a new boiler.
I think, like the OP, what I really don't understand is people prioritising extravagent gifts, and gifts to people who'd be happy with a card, over financial security, so ability to pay for things that benefit the whole household, year round. Dull but very reassuring.
I suspect a lot of people on here are the very smart budgeters who have it all taken account of and itemised and have had the forethought to be able to bargain-spot throughout the year too. In which case I'm just a bit in awe.