Cook the turkey, take it out and cover with tin foil and a couple of clean bath towels to keep it hot for up to 2 hours.
Have the potatoes par boiled and toss them with the goose fat, so they are ready to go in as soon as turkey comes out. I like to have them hot going in, but doing them beforehand (say Christmas Eve) is fine too, just add an extra couple of minutes to cooking time.
Have the veg for roasting ready as well, that you have steamed them for a few minutes in advance and then tossed with the herbs and seasonings (including some satsuma juice for carrots, yum).
Both of those will reduce cooking time for the potatoes and veg.
Brussels sprouts can be steamed, frozen peas can be boiled, carrots can be glazed (gently cooked with some onion and a tiny amount of liquid) all on the stove top. Cauliflower cheese can be made, possibly by having the cauli cut into florets, by cooking the cauli and sauce on the stove top, and just popping under the grill to get golden while you are clearing starters and getting the mains put out.
Gravy can be made in advance and just add in the juices from the meat as you reheat it, again just while you are clearing/serving.
Plates and serving dishes could be heated in the oven (turned off - residual heat is plenty) while you eat starters. Or soaked in hot water in the sink and quickly dried. Or run the dishwasher to have them hot and clean just when you are serving.
For large groups, I would tend to have either a cold starter that you can have plated up in advance, or else something like a soup that only needs a large pot rather than anything needing oven space.
Ham - cook it in advance, slice it, and reheat from cold by steaming with a tin foil cover over the meat to prevent it getting soggy. Could do the same with spiced beef.
And if you have that large a group, plan on having 2 or 3 sets of each dish spread around the table (or serve each plate in the kitchen), a few salt and peppers, at least 2 jugs of gravy etc.
I would also tend to make sure everyone gets one roast or hassleback or duchesse potato (whatever your seasonal preference is), but also do a pot of mashed potatoes to put on the table to reduce pressure on oven space. Have more seasonal specials if you have room - but perhaps have a second tray of roasties that goes in while you eat starters that will be ready as people are starting to look for seconds.
And also think about the trays you use - can you fit more in the oven by buying those disposable trays and fitting 2 to a shelf? SO you could have smaller amounts of 2 things, and have a second lot to go in as you serve up to be ready for seconds if needed? Or maybe having some things cooked in advance (that morning, day before etc) and just needing reheating rather than full on cooking? So they could go in after potatoes or whatever?