Before you start demanding a refund, what is wrong with the P/C, does it work?, has it broken down?, is it the wrong spec?, if not is it just the software that is missing and if so what software? Mesh actually do make a good P/C and for the money use good quality parts so you would be better sticking with them, or have you just seen a better P/C for less money?. I'm not being funny when I say, that but this is what someone could think if the P/C is working correctly.
Second point,if we all took note of "fitfella 29" then no one would buy from Mesh, BUT if we took note of GANDALF we would all buy our P/Cs from PCW and so it goes on and if you had bought from Campus you wouldn't have a P/C.
Put a posting up telling us exactly what is wrong with the P/C and then someone can mayne advise you on your rights.