Employer View: Auto-enrolment is adding fees to our existing pension scheme

For the last 15 years my small company has offered a matched 3% contributory pension scheme to all employees after a 6 month probation period, so auto-enrolment just seemed like a case of ditching the probation period. Each employee would sit down with the pension advisor, choose their risk profile, and select their fund make up.
Our scheme exceeds the minimum auto-enrolment requirements. EXCEPT - that in order to comply, it has to provide a bunch of extra reporting to the government. Result - we will be hit with a £100/month extra admin fee.
The company FA has suggested transferring everyone to another scheme that has lower charges, but I'm not happy about forcing that on my employees. Has any other employer been faced with this, or have employees been forcibly moved from perfectly good pension schemes?