I think it depends what you are driving too.
In a panel van you seem to be less likely to be bothered than in a motorhome as a motorhome stands out.
Although having said that we have never been bothered in either but seen others being bothered.
If we were I think I would be as polite as possible and unless I had a drink would just move on a little if the ''we will be off in the morning without a trace left IM knackered excuse did'nt work''.
I would'nt feel settled after being asked to move on anyway.
One thing that annoys me though is here in the UK you can only sleep for two hours at services but in Europe you get a good nights rest.
Its daft as you think like and safety would come 1st.