This is a random one but wondered what your favourite filling is? Hoping to see something pregnancy craving odd 
I got the bits to make a sandwich, but left half to share so others could taste the best sandwich in the world. Well to me anyway, will have to wait for further votes.
It started off with M&S in house granary bread, smallish loaf, apply mayo instead of butter, half an onion (that's always precut in a tub) apple smoked Wiltshire ham, bit more mayo, then peppery salad leaves.
You could add mustard if you're a fan, the mayo did it for me. Was going to leave 3/4 of it so everyone had their fair share. DD will pick out the onion, or DH will for her.
To buy it I think you'd be looking at £2/3 in an artisan food shop.
Loaf £0.99
Red Onions £0.80 a big bag
Peppery Leaves £1.50
Ham £2.00
Mayo £0.79
All from M&S, will do about 6 lunches if not more. Plus I got a cucumber for £0.50. There's loads of leaves left, we get our red onions from day Sainsbury's they're always on their way to onion heaven, but these were perfect & a big bag. £6 including cucumber, so £1 a lunch with left overs.
I know for most men bacon is a must. Something in male DNA unless practising Jewish or Muslim or Veggie.
Bliss.