Vegetarian cauliflower cheese cottage pie

I spotted this recipe for a cauliflower cheese cottage pie whilst dozing in front of Something for the Weekend (now resurrected as Sunday Brunch on C4), a few weeks ago. I don't really know why I was so taken with it, but I guess it has strong comfort food appeal and looked to be easily adapted for a non-meat eater too. I wasn't sure how a creamy topping would work with a mince base, but it turned out that the answer was 'really well'. The only downside was how un-photogenic my plate of food was, though it's heartening to see that the BBC didn't do much better.
The original recipe is on the BBC Food website, and my version is below.

Recipe (enough for four)

300g Quorn mince (or any other veggie 'mince')
1 carrot, finely diced
1 small stick celery, finely diced
Half a leek, finely sliced
1 small white onion, sliced
1 tsp dried mixed herbs
2 tsp fresh thyme leaves
1 tsp ground cinnamon
3 cloves garlic, crushed
1 tblsp tomato puree
3 tblsp sunflower oil
Around 4-5 tblsp water
Salt and pepper to taste

1 regular cauliflower
300ml creme fraiche
150ml double cream
1 egg yolk
0.5 tsp English mustard
Around 200g grated cheddar cheese, with a little extra for sprinkling on top
A bit of salt and pepper to season

To make the cottage pie base, gently heat the oil in a medium pan and when it's warm add in all the chopped vegetables and dried herbs. Cook over a medium heat until the vegetables have softened (around 10-15mins), and then put in the veggie mince, thyme, cinnamon and garlic. After about 5mins add the tomato puree and water, give everything a good stir, and season with salt and pepper. Keep things on a gentle simmer for a further 10mins or so, check the seasoning, and then leave to cool.
While the mince is cooling, make up the sauce for the cauliflower by mixing together the cream, creme fraiche, egg, cheese, mustard, and a little salt and pepper. Cut the cauliflower into medium florets, and cook in boiling water until it's tender and almost falling apart. Drain the cauliflower and allow it cool down for a bit before mixing it all into the sauce.
Assemble the cottage pie by putting the mince in the bottom of a deep-ish baking dish in single layer, and then spoon over the cauliflower cheese. Finally sprinkle a bit of cheese over the top, and bake at gas mark 6 for around 30-40mins until it looks lightly golden brown.

Serve with some green vegetables, ideally in mildly autumnal feeling weather.