Can I ask the estate agent the ID of the viewers and bidders?

I would say feedback on the profile of the viewers/bidders is essential. We sold a house a few years ago and the agent was easily able to tell us which viewers she thought were serious and why. For example, some were classic tyre kickers who viewed every property in the area as a Saturday morning recreation! Some had proactively registered their interest in the property type and area and had travelled a distance specifically to view the house. Likewise, proof of funds sorts out the wheat from the chaff.

For potential tenants, it's even more important. You want to see evidence of ability to pay and references from previous landlords or other living arrangements.
 
The conflict of interest is not on the closing of the sale (when vendor and agent get a fee) but on resale when Murkey title may cause a sale to fall thru
Can you explain how there is a conflict of interest there for the vendor's solicitor?

Can you try that again please, the point isn't clear. Are you now saying your concern is for the vendor and not a reckless purchaser who decides to purchase a property without seeking legal advice?