I think first of all you should consider that the advice given on this site is the opinions of the individuals that post it and not necessarily from experts in electrosurgery. The other consideration is that nobody on this site has advised you to do anything - just made you aware of potential issues that could occur theoretically speaking.
On the issues of compatibility I was not inferring that similar electrosurgery units were compatible in the sense they should work together and be used for dual operation. Just that it may be possible for currents on two similar units to 'cross', as Rojo puts it, if the outputs are compatible i.e. can be detected/measured by each unit and a return path is completed.
However, based on what you say, I think it wouldn't do any harm to approach the sales representatives and clinical trainers from Valleylab to discuss any concerns about the use of their equipment.
If you still have concerns then perhaps you need to speak to an expert at the MHRA for advice, guidelines or recommendations concerning technical aspects of the use of electrosurgery - remember it is a clinical decision to use a device or not - the clinicians, theatre nurses/ODPs should be familiar with the equipment and be aware of what is and isn't good, bad or best practice. It's their responsibility at the end of the day, not yours, to decide what's acceptable use of equipment or not.
To partly answer your question - yes there have been publications from the MDA/MHRA on the technical and clinical aspects of electrosurgery and such things as posters highlighting best practice/responsibilities regarding electrosurgery.
