The countdown to Christmas is a fun activity when you live with young kids. You have all November to craft your own. In fact, if you wish to get the advent house or the bucket advent calendar you have no other choice than making your own since they are out of stock at John Lewis. They may get more since you can leave your email but I would not count of that.
For the house, you could start with a paper or a wood house model. Get a good supply of card boards and foam core to add details to the house. Use paint, gift wrapping paper,and small ornaments to decorate every window. It could be a fun weekend project for the family.
The bucket pennants is easier to reproduce than the advent house. Sadly, I am not sure that you will save money by making your own. To make your own, shop for 25 small decorative buckets, look at scrapbooking items to craft the date tags, and find a festive large ribbon.
Feel free to send me pictures of your advent calenders. Do you follow the advent calendar custom? If you follow it, do you put a toy, a treat or an act/goal to your kids?