Hello there!
Business Economics is a less rigorous degree in terms of mathematics. There is more emphasis on understanding the process via graphs and simplified equations. Traditional Economics degrees are very technical. It's not unusual to see students who only know how to handle the mathematics without really understanding the theory behind it. i.e its very different from Business Economics.
The reason you have not been able to land a job as an economist is because you lack the technical part, which is exactly economists do. In many cases, a postgraduate degree in Economics is required for a traditional economist positions. Some may take a fresh L100 graduate from a top rated programme for a year or two, before sending him to do his masters and even PhD.
Diploma in Economics is a conversion course designed for graduates who did not study traditional economics degrees, and want to do a postgraduate course in Economics. It is also suitable for you because it will be a requirement for you to do one should you want to do a masters degree in Economics. It will give you the technical foundation required for the masters. It's essentially technical, core undergraduate modules such as micro, macro and econometrics.
I would not recommend you to take the diploma as it is unlikely to suffice as a credential for an economist position without a complementing masters degree. Moreover, you expressed reluctance to read a masters degree because you didn't think you could handle it. The diploma is also technical so you are likely to struggle with that too. Finally, if you think the technical aspects of a masters degree are too much for you to handle, then you should reconsider your choice of profession. It is very technical.
Hope this helps. Good luck! :-)
This was posted from The Student Room's Android App on my GT-N7000