I like the Hairy Bikers' mincemeat from their Christmas cookbook - I have some left in the cupboards from batches in 2015 and 2017 that I will use up this year (last year, I found a jar from 5 years back, and it was just soooooo lush!! Really keeps and matures well, I keep it in a cool dark cupboard). The pastry in their book is nice because it has orange peel in it - but I also use a mince pie pastry that DM got at a cookery course in a hotel years ago (hotel chef's own recipe).
For sausage rolls (what we don't buy at M&S), I get a pack of Jus Roll puff pastry for the skin (I am not great at shortcrust, and useless at puff, from scratch!). The stuffing is made with sausage meat from Supervalu (the old Superquinn sausages recipe) and I add thyme, and sometimes some caramelized onions or some chilli to that.
DD used to make Spiced Christmas Cookies before going to primary school, which were lovely. I must make those again - the recipe is handwritten in a book at home so I'll try and rummage it out. Nowadays, she makes a kind of cookie that you slice off cookies from a roll of dough - the basic recipe can be tweaked to make orange and lemon, chocolate chip, double chocolate chip (chocolate dough and chips), or just plain. And the roll of dough can be frozen - so handy to make a large batch and only cook half, keeping more for later when guests arrive at no notice or if we have no time to bake properly for Santa on Christmas Eve.
We also sometimes make a Christmas Pudding - but a sort of rocky road version. This is so popular that we've made it as a Communion and a Confirmation cake at other times of the year in the family as well. Use plenty of layers of cling film to line the bowl, but it is really effective with the dark chocolate base and then white chocolate "custard" flowing down over it!
A couple of years, I made candied peel (back in the days I had time!). I'd love to make Orangette chocolates doing that. But chocolate truffles are great when you have less time - I tend to roll them in cocoa powder to finish (and use a pair of plastic gloves for the rolling of the balls to save the mess).
A favourite "using up leftovers" recipe is a Ham and Stilton gratin from Good Food (maybe 2000 or 2001 December edition - not Christmas prep but Christmas leftovers). Basically, shred your ham, crumble your stilton, thinly slice your potatoes, strip thyme of its leaves - in a well buttered serving dish, build up layers of ham and stilton seasoned with pepper and thyme, then potatoes, then ham and stilton again....pour on hot turkey stock, bake in a hot oven until done (about an hour) and eat.
I'd love to make my own cheese straws, and do various other bits. But most of my other cooking is the basics - turkey stock, proper roast dinner, turkey sandwiches etc. And we don't have to entertain too many.