As per CIC website, 12 months of continuous experience with one employer in last 10 years. Now, in your case, if the Employer name on Salary slip and Offer/Appointment/Contract letter remains same for 12 months, you are good to go.
Let me explain it a little further.
I've been working with Client A. But changed my employers .
Client A - employer A - 6 months.
Client A - employer B - 6 months.
Client A - employer C - 6 months.
I worked on the same position with the same team.. Just my employers changed that is on whose payroll I am changed.
Now for these employers there was a vendor in between. So I have letters for both the vendor and client from this year and last year that I've worked with them on a project named 'xyz' fron the past months.