Kinky good question about treats. I feel a bit of a fraud on this thread as so many people are genuinely struggling with bills, and we are feeling ok. However although this year we are both employed and are covering all our costs, I want to ensure that the basis of our family spending is frugal, so that we value and appreciate the luxuries that we're currently able to have, knowing that we could some day have to cut back on them.
We have one meal a week which we call 'treat night' if it's a meal out or 'cheat night' if it's a takeaway (which we usually over-order so that we can have leftovers for a couple more meals). I think I might reduce this to once a fortnight because it's not a healthy thing to do, I'm supposed to be watching my diet due to chronic anaemia, and we could have a nicer meal out with the money saved.
For me, frugality is about spending money only where it has a genuinely preferable or unique impact to spending time/effort/energy - in this way you might not feel like you're "going without" by taking a cheap/free option but rather you're "making better choices". This is the 'own brand cereal' argument - is the marginal enjoyment of Rice Crispies over rice pops actually worth the extra 30% of cost?
So: doing an exercise video to warm up, or cooking a big batch of food to use the oven most efficiently (versus putting the heating on) are both things I want to do anyway.
Getting the family together in one room to play together, read books, or watch a film snuggled on the sofa with the gas fire on, rather than everybody being on their own in different rooms with the whole house central heating on.
Going out to the park and enjoy using the facilities like playgrounds and local nature reserves that you've already paid for with your council tax, rather than paying more to go to an 'attraction'.
Using the (still free/subsidised) museums and galleries in London. Take up memberships where you'll actually use them - e.g. the London Transport Museum entry fee is the same as the annual fee - the only difference is you give them your name, address and signature. And we haven't actually had any junk mail from this.