It's a toughie when you are in that position, giving an hourly rate is a pig, I hate doing it, if you tell them you are going to charge £30 an hour they'll have a fit
But that could well be the rate at which you could earn on a priced up job.
Ultimately you are better if you can price it up.
If the job is one that just the thought of it leaves you groaning inside, and it is for a long standing customer, you have to do your best and try and 'load the bases' in your favour.
Point out all the problems, access, ladders, pig pen clean and so on. I try to tell them that as it is just a one off clean it is going to be expensive, that it will be close to three times what you would charge if it were a monthly clean, particularly if you can't use ladders(WFP notwithstanding)
But you still managed 20 quid an hour for the job, much easier if you can price first, it is just so hard to justify charging £25.00 or £30.00 an hour, the customer won't understand, they'll look at their bill and think, "Thirty quid an hour! Hell, thats £240 a day, thats £1200 a week!! The cheeky sod isn't getting away with THAT
"
It doesn't work that way in reality of course, but you can't sit them down and explain that.
But you live & learn, next time he asks you, regardless of how good the regular job is, tell him you aren't interested (unless he is having it done at least 3 times a year) the job is just too far underpriced.
Time I was at work!
Ian