Hovis granary flour

It's my third attempt at using this flour. It's always disappointed me so far; the dough has been horrible to work, and the bread's been too heavy, and less tasty than you'd expect. So I'm trying with a long sponge time, to see if this will work better.

Sponge
300g Hovis granary flour

Per 100g
Protein 14.7g
Carb 64.3g
Fibre 5.6g

300g water
3g sugar
2g dried yeast (that's about half a teaspoon)

The small amount of yeast is designed to lengthen the sponge period. I'm starting this at 10:30 in the morning, and I want to leave this for at least 8 hours. It's the last of the granary flour. At the second stage I'm going to add strong white flour.

Here's the sponge, looking porridgy. I'm leaving it at kitchen room temperature, which is about 15C today.

And here's my lovely new electronic scales, which enable me to give such precise quantities.

 

Update 1
Earlier than ideal, at 1700, I've added salt and 150g of very strong white flour. Didn't need to add any more liquid. The dough kneaded well, but a little wetly, and I've formed it into a bloomer, slashed lengthways by way of variety. I think it'll be ready for the oven by 1830.

I think one of the things I dislike about this flour is its colour. I've done a bit of research, and although the recipe is secret, it seems that the flour is basically white, coloured with malt. I prefer Allinson's Seed & Grain flour, which doesn't pretend to be anything but basically white. The colouring seems to make the dough heavier, while S&G is lighter, with seeds etc floating in it.

Update 2
So, I put in the oven at 1820, using a stone and no steam or eggwash. 10 mins at 7, then 30 at 6.  The loaf had spread worringly, but sprung well.

It now weighs 640g. It might be interesting to analyse percentage of water in finished bread: it must relate to the lightness, although I suppose you'd also need to measure the volume. Doing the sums (ignoring sugar, salt and yeast) this bread is about 30% water. I've no idea if that's normal.

So, how was it?
OK, but no better than OK. The bits of malt don't seem to act like nuggets of flavour as they should. Maybe that's because of the long proving - their flavour leaches out into the dough. The crumb was light, and the crust was soft. And it must be a symptom of something that the uppercrust was poorly attached to the crumb beneath, as if there's some late and anomalous rising at the top of the loaf. I won't use the flour again. I think a better approach would be to use normal flour and add the malted grains late, at second kneading.