Ian, thanks for the pics – I hope soon to have the site on a more powerful system where photos can be uploaded into the forum.
And yes you can sow and plant into this. That is one main point of my gardening method, sowing and planting into a surface enriched with (ideally) year old organic matter, and yours fits the bill. It sounds like you are already doing well and you should find less anual weeds germinating, but there will be some in that manure. However it is easy to scuff around, hoe or whatever on a dry day when you first see tiny seedlings, so they never get established.
I was just picking lettuce on my dig/no dig experiment and the lettuce planted into cow manure yielded 680g compared with 560g on the dug soil, with manure under a spit of inverted turf. Direct-sown carrots and parsnips are coming up fine on both beds.