I've probably got in a muddle by needing to research everything properly...however the sequence of events:

 

The builder underestimated how much spoil the piles ( he subcontracted) for the hayshed extension would produce, went on holiday, had to isolate, and we lost the weather and the grab lorries trashed the site. He left one chap to try to dig the utility trenches alone and it became like the Somme and he couldn't make progress, so I asked them to stop as I realised the decision making was becoming suboptimal and the chap was demoralised.

 

He was encouraging me to do the larger footprint without planning permission, but the prospect of enforcement made me lose too much sleep!

 

So... I'd like to do the foundations up to floor level, but I haven't begun to research how to do it yet...because I'm not certain what would be the best construction method.

 

I'm afraid of inviting construction lorries on again until spring when the ground improves. The temporary entrance hasn't been good enough to cope with the winter.

 

I think I'll need to pump it to keep water away, as the clay is built up where the infamous trenches were dug. It's terrible to dig into at the moment. Gus has given me lots of advice about frost protection of the stable foundations at the junction between the building and the beam.

 

Hopefully it won't be open like this for longer than 6 months, however, building the structure could be 1-2 years. 

 

(I can't apply for planning permission until we have a completed dwelling. If I use the smaller footprint, which has planning permission, I can  a) create the second bedroom by removing the east wall of the main stable, or b) create a very small room which will have to be demolished later). 

 

https://www.machinemart.co.uk/categories/?search=Dirty Water Pump
 

I prefer the lay flat hose rather than normal hose to connect up.

 

Don't buy a cheap plastic submirsible pump, even if it claims to be "dirty water"  I did, and found the plastic impeller fell apart when trying to pump even small stones in the dirty water.

 

When I complained to the supplier, they replaced it free, and did not even want the old one back because it had been used with "dirty water"  I later repaired it by swapping the impeller with another pump with a failed motor.