I'm baffled by one or two things on this loco, the smokebox saddle doesn't seem quite right, I think it should have a flange all the way round...
I replied at the time of your question to the effect that the front and rear flanges/bolts could not be seen as those fastenings were hidden by cover plates. A trip to Didcot earlier this summer has enabled me to include some suitable photos.
In this photo you can see the gap between the front face of the cylinder block and the cover plate... plus the bolt holes in the front flange.
This photo is the rear face of the cylinder block shown in the photo above. Here the cover plate has been removed albeit there is the remains of a 1/4" BSW bolt in the vertical face of the rear flange.
This cylinder block is sans loco... and offers an opportunity to see the joint between the two halves of a Churchward-style cylinder block. Also visible are the threaded holes, on the vertical face of the bolting flanges, for the bolts which retained the cover plates.
All photos my copyright - retained.