I respectfully disagree. The WHOQOL and SF12/36 are ... not terribly useful outside of a purely medical context. The questions are focussed heavily on symptoms and loss of function. Even in the context of the WHO-ICIDH they do not cover the levels of participation particularly well - and hence cannot really measure anything positive about quality of life. That is, if you are measuring some group that has some medicalized condition and you are expecting functional or symptomatic improvement then these will do. For anything positive, they really won't.
Without knowing more about your project it is hard to give guidance. However, some good starting places would be the QOLI, SWB scales, hope scale, etc available through http://www.ppc.sas.upenn.edu/ppquestionnaires.htm. You may well need to go farther afield if you have a particular subjective conception of wellness in mind.
Thank very much Bruce, I completely agree with your opinion, if the researcher is not interested in the improvement of quality of life in patients undergoing any type of medical intervention, he should rather use some of the options you mentioned above.
Yes, thanks a lot bruce. L agree with you. But it is about improving the quality life of the people who are undergoing medical intervention as said by augusto due to the risk factors of chronic diseases of lifestyle and moreso low socioeconomic status individual.