Thanks for your enquiry.
There is a clear conflict of interest in the same Solicitor acting for both of the parties at different times, so he/she certainly should not be acting for the husband, even if he/she has moved law firms.
This should be raised by you (if you are the wife) with your Solicitor.
If the matter is not resolved, you should make a report to the Solicitors Regulation Authority.
I hope this answers your question, and if so, I would ask that you leave positive feedback.