So I went to see the lady after arming myself with the knowledge from here. Firstly, I went over to the house that had been cleaned by the other guy (it is actually one of my window custies!)
I noticed that only half of the house had been 'washed' and they definitely used SH as the lead flashing all along the porch has turned a rusty colour in places, the brown electric meter door seems to have this white chalky substance etched into it and all the daffodils were half dead underneath. (See pics)
So I explained to the lady that it seems the guy has little knowledge about what he's doing. She now realises that £250 was for half of the house and would need to pay at least £500 for the whole house going by hypo guy's rate. Then I explained about the quick fix SH and the longer term biocidal treatment. And that the chems cost a lot more than the hypo that the other guy used (she knew that he bought the stuff from this "farmers place", he actually told the customer.
So this might be a great opportunity to get started properly by getting the proper gear, up the insurance and experiment on my dirty house first.
Here are the pics of the house that the hypo guy did
