This wasn't aimed at Nationwide. but those bad nationals are out there and the rep of other nationals will rub off on you I think.
I've not looked at your concept and was commenting on observations of the companies who are out there now.
sample scenario -
Harrys furniture (fictional company) have 100 stores around the country and want them cleaning for £10 per store
store in Bradford has 5 windows and a door = £10 for Bradford contractor
store in London has 15 windows 3 doors and a nice shiny neon sign that they want cleaned = £10 for London contractor
store in Liverpool has 1 window and a door (which are usually boarded up
) = £10 for liverpool contractor
other 97 store with similar variations
or you get each contractor to send you a price they need for the store which opens it up to regional variations and will encourage contractors to come in with a high initial price.
I'm not being funny at all but can see the logistics being a bit of a nightmare. Having said that - I'll have a look and may sign up
good luck