So ...
As of Monday evening the hire van goes back and I have a week to get my van returned, give it a thorough check over and if ok start arranging for bits and repairs.
By this time next week I should have either decided to not keep it or be part way through repairing it. (Most of the work being done by Dan the Man, me sharing his van and using a backpack out of Mrs. Gold's little car. Three or four barrels and a backpack so about 100L.)
Today I tried it out on my own house which is a 3 bed semi with a high rooflight but no bays, porch or conservatory.
From opening the tailgate to shutting it took 13 minutes for the house plus 4 minutes to change poles and move the backpack for the rooflight.
I used 12 litres for 12 windows/doors and wiped the downstairs cills with an old towel to save water.
If I was charging I reckon I would ask £16/18 if among others nearby.
So I hope to get north of £100 out of a three hour half day with driving included.
We shall see ...