surely by using the GC to the amount lee does then the money being in his bank quicker than B/Tansfer ,he gains interest on his account which would cover or help cover transaction payments 
90% of customers pay within 3/4 days though. GC is7 days I think.
Cash flow - I guess you'll have a certain % of your turnover outstanding, that'll be fairly constant, raising slightly throughout the month with a higher portion coming in around the end/beginning of the month. That % grows as you do. Switching everyone to direct debits would fix that percentage and reduce instances of debt write off.
Fees - 1% is pretty fair. Don't forget:
The Santander app is rubbish, paying in is a pain often taking 10-15 minutes at the machine and the search facility for transactions on the website is rubbish. You get what you pay for I guess.
I agree 1% is ok, but don’t forget under £20 it is higher as the minimum is 20p.
I offer it, but I see no benefit in moving someone who pays within 48 hours to 7 days with Gocardless and to have to pay for the privilege. Each to their own though.
It's true there's no benefit if that's the case may I ask you do you allow 10 working days for payment or are you more strict on that?
One other thing as you got quite a few vans going and obviously a lot of customers I can tell you from my point of view Cross referencing BACS payments and things like that does take up working hours I know I can do it when I'm home and stuff like that but it still is annoying now your scale I think it will be super annoying but then again it's just business isn't it. I think that would be another benefit it would save some admin for you well quite a lot obviously. And then you have the unidentified BACS transfer which you can't identify and you only find out later.
I have my fair share of "window cleaner" reference
Probably from the spouse who hasn't paid before
Gocardless does help eliminate that what's your thoughts