Nice! Thoughts Sam?
Stealing just the kitchen worktop depth from the third square and introducing some storage space instead of larger WC/bathroom would get my vote. Work to the existing verticals and then make a feature of a vaulted roof (if possible)? In the short-term the kitchen worktop area could be office storage with the water already accessible behind?
Cooker and sink should switch (fire). Talk to East Devon about any M (wheelchair) requirements that they might now be applying. Unless you're non-notifiable?
Or could you put some sheep in there for an agricultural PD application? 😉