When you have friends over for a roast dinner, you sometimes want an alternative to a nut roast or a quiche. Here's a menu I've found works well because the Chestnut and Vegetable Pie is special by itself, but with the Pork Tenderloin it enhances the overall 'wow' factor.
Roast potatoes or mashed potatoes
A green vegetable like broccoli, or sprouts e.g. Sprouts with Crumbs
The Chestnut and Vegetable does require a bit of time to prepare the vegetarian/vegan pie - but it gives you something to do while the meat is roasting! You need to allow 50 minutes for the pie to bake, so make sure you start the preparation early. I think the chestnuts in the pie go well with either turkey or beef.
To save time you could just serve the Pie and the Pork with some simple green vegetables like broccoli.