Hi tabhar2000,
Please go thru' the caseworker's manual couple of time.
http://www.ind.homeoffice.gov.uk/docume ... rguidance/
Specifically
http://uk.sitestat.com/homeoffice/ind/s ... iew=Binary
What I understand from this is that they conclude if your job is a degree
level job from your responsiblities stated in the evidence you provide.
I understood from one of your posting that your experience letter was not
signed, I think it is better if you get it authorised from one of your manager.
Provide as much evidence as possible, links of your company web sites.
I produced print outs of job posting from my company website which
clearly stated the eligibility to apply for such position should be Engineering graduate.
Provide some references like your manager's contact details.
I think you can not provide additional evidence, hence only way is to
state everything in the cover letter.
Also answer any obvious question in your cover letter(don't hide any thing)
Eg- Give a convincing reason why your experience letter was not signed
Wish you all the best!