I've been asked to look into this at work, but we have no HR dept (or similar) and I'm neither a lawyer nor a HR professional. We do have a regular legal firm we use (large national company) but I haven't been impressed with the recent service and I don't know if they are specialists in this area.
NC because my boss would be raging if she knew I was asking MN! 
The company I work for started 20 years ago. Recently it received advice, as part of a review, that some longstanding contractors might actually be employees (not an IR35 issue, this was flushed out during an IR35 review). I've been asked by the directors to get a second legal opinion, focusing on employment law (not tax), but this is massively outside my area of expertise and I don't know where to go to get good advice. Can anyone recommend a legal firm who specialises in this kind of advice please?
Happy to PM more (outing) details to any of the employment board regulars that I recognise - I lurk on here quite a bit.
Many thanks for any recommendations 