Lee, just stick your price in mate, don't worry about it. If he asks how long then tell him.
If he doesn't like it, or he thinks he's paying too much, he can get other quotes. Simples.
Personally, I always do the quote then and there, with the customer. For me it's
£x per section of guttering clear out
£Y per section of guttering clean and clear (this will depend on how dirty it is, access etc)
Windows extra
I count up all the sections, write it all down on a piece of paper, add it up, show it all the custy and that's the price!
If he's lucky i'll throw in the garage door and downpipes for free.
PS. I think I saw that you can now buy the drum part of your Atom with the side entry port already fitted!