Tried them - 4 candidates but not one who could string an english sentence together. When we open our Punjab or Zimbabwe office I'll be straight back on to them.
HNC/HND, BEng/BSc or MEng/MSc in a relevant engineering discipline. City & Guilds also run engineering courses but they're not accredited anymore. These courses are very general and cover 3 different disciplines; a lot of work for something the institutions can choose to ignore.
Alternatively, you could get yourself some CAD experience and then look for somewhere that is willing to train you.