Well Dave?
I would think you rich kids in the Southwest must be cleaning up on being host to 2million tourists a year!
C'mon don't be shy. Make it £75, if they've got money to spare, then make it £80.
They're not going elsewhere for a quote, are they?
So, if you don't hear a positive response immediately and you want the job, drop it down to what you know they'll go for.
If you get it....You owe me..Naa...You'll get it.
If they accept first time, it's yours. If they think it's too much....easy peasy..You say, Oh thats just first clean! Don't worry, it'll be less than that regular. Make sure you get the deal to do it once(cos no-one else will), then you'll know exactly what to charge.
Pj
ps Don't forget me