I am going to start my MBA program at a university in London in September. My situation is, I have also gotten the chance to work at an industry that I really like in England this summer, before school starts. The employer's HR department thinks I can just enter the UK using my student pass and work for them before the school starts, since the student pass will allow me to work.
My concern is, from what I've read, the student EC will have a start date which is usually 2 weeks before school starts. Well, school starts on Sept 18, and if that means I can only enter the UK on Sept 4, I won't be able to enter the UK before that, which means I can't work.
So my questions are:
1. Is it possible to ask the British Consulate to put the start date in my student ec as far ahead as July, even though school won't start until September? Will they even consider this request? Has this ever been done before?
2. If the above option is not possible, any suggestion on what me and the prospective employer should do? I thought about TWES, but that scheme will force me to leave the UK after the work is complete, which means I can't start school.
Any help would be really really appreciated.

Thank you very much in advance!
PS: I'm a total newbie in UK Immigration rules, so apologies if I'm asking some obvious questions. I searched the forum but couldn't find anything that can assist my case.