Its not must to send employment contract with your experience letter, if you see they actually only ask for the employment letter which shows the job duties, annual income, and job status full time or part time plus payslips. All the applicants who send further documents like there achievement letter etc etc they are not must but they just put some weight that your job is geniune. In your case you can only send the experience letter no need for the employment contract. But if you want to send the employment contract for the GLS as its already mentioned about it in employment letter then just send an explanation statement stating that you are working with CLS under the GLS residence visa its not a big issue you are working and living legally so dont worry about it.
The VO London requires says the following for point#7:
For you, your spouse or common-law partner provide:
•notarized employment contracts from your present and past employers, accompanied by an English or French translation
•original and up-to-date letters of reference from your past and current employers. Letters must be written on company letterhead and show the company's full address, telephone and fax numbers, and be stamped with the company's official seal.
Letters must include all of the following information:
•the specific period of your employment with the company
•the positions you have held during the period of employment and the time spent in each position
•your main responsibilities and duties in each position
•your total annual salary plus benefits
•the signature of your immediate supervisor or the personnel officer of the company
•a business card of the person signing
If you cannot provid
as you have stated earlier that we do not need to send in the employment contract...i just need to make sure that it is not a must although stated in the requirement above.. please advice