I'd have a bit more faith in everyone to do the right thing.
There is a lot of money in the processes behind selling a house and no-one would be wise to compromise their name in what is a very competitive market.
There are players at every level who are right there, waiting for someone to slip up, so they can increase their turnover. It would be like losing your place in a long queue if you oversaw something and people made a big deal out of it.
If you imagine a newspaper headline "Dodgy dealer diddles innocent family with nasty mine working riddled house" It would be instant game over locally. People have to be whiter than white in what is a competitive market with some seriously deflationary pressures.
I'd wait to see the report. Someone will have decided on a solution, someone will have put their name to it, Building Control would have turned up to see they were gunging the right house and all will be dandy.
If something does screw up, which is highly unlikely, someone's insurance will get nailed and the people who undertook that work will have considered that, before they put their names to anything.
Anyway, no-one has been ripped off yet. If I was the seller of the house, I would have got the house drilled and upped my price by the cost of the drilling. If it required remediation, I would have had the work undertaken and balanced the price rise with the loss myself. I would have even considered haggling with the remediation firm over some sort of deferred payment for the works.
If you sought to sell prior to drilling, the house would have been "worth" as much as the worst case scenario. ie:- a house which needs to be demolished and a building plot with a mining feature which needs remediating.
If you sought to sell prior to paying for the remediation works, the value would be minus the cost of that as well a "hassle penalty".
Having all the work done, the guy has a house with a piece of paper saying it's abandoned mine proof and if it isn't, the work is insured. One might philosophise over whether a house with this piece of paperwork is more valuable than one which may have an outside chance of a hole under it, but was not deemed necessary to have a search undertaken. Either way, the seller is probably going to lose out by a nadge.
It makes you wonder what took place at the original purchase....was it during the times of lenders not caring about the risks of working, or did someone get diddled....?
The alternative which is pretty popular, is that the owner lets it out and rents what is a pretty much unsaleable property at it's market value.
This is precisely what happened to me when I was renting in Redruth. 3 of the doors in the house started being a problem to close and one day I looked out the window and the back garden had disappeared.
Mine workings do not affect the rental potential of a building! Unless they have started causing problems.
I suppose it's the duty of care for the landlord to inform the agent and the agent to inform the tenent, but in the case of my agents (who had all the bits of paper and all the letters after their names) they just saw fit to oversee it. After all, the client of the estate agent is the landlord, rather than the peasants who pay for the whole gravytrain.