Dave, it is good to belong to an organisation. I belong to the Confederation of cleaning Professionals, but I must say, I have not had one customer ask me about it, but then again they can see the badge on all my marketing.
Dave you can definately earn more. You said you are stepping up in the market, well you've earned it, show your experience and put up your prices.
Last week we did a 4 bed detached (empty let) and got £412, 5hrs work, we are doing a 3 bed let for the same couple, £300, they have another 3 properties, I hope they leave soon!!!
My average per house/job is £325. I do this part time as I run another business as well.
Mark