Just a student but I mean if you are working for £30 a day then try going up to £40 a day and see if you are still getting work, then £50 then £60 and just base it on that. You'll soon get a feel for how much you want to earn and how long each job will take, so if you want £50 a day then you know I mean after 6 years you must know that will take me 1 day and a bag and a half of plaster plus a few quid in fuel.
The supposed going rate is irrelevant because it is only about the price you can obtain from customers not what another plasterer in Kent can get, the going rates for him - well you are not him and you are not in Kent. It is like a guy in Washington DC giving you his going rate. You don't have his skills or personality or geography.
I once had this explanation given to me, "My Saturday work is priced like this. £150 for me (extra if labourer is needed), £50 for materials and £25 for the van"
Whether you agree with the figures or not who cares. The method is sound. He isn't working on the Saturday for less than £150 for himself and a few quid in for the van while he is at it.
I mean, I guess, what the hell do I know? Absolutely nothing.But its how I'd do it. If and when I have the chance.