Offer accepted on a house. They have no extension papers or PRC certificate

I have had an offer accepted on a semi detached house. It was offers over £260,000. I had an offer accepted for £261,000. It was last sold in 2015 for £255,000 with the current extension, and from the old photos appeared in a lot better condition.

The house size is decent, 4 bed, kitchen opens up onto living room with another reception and utility and double garage and large garden.

I know over the past at some point between 7-15yrs ago it had a double extension at the back. Also the house I think used to be an airy house and I have heard that the walls were completely taken down and rebuilt. The house has some damp possibly due to blocked drains or roof tile and small crack on the landing wall and one of the bedroom walls. Also there is some damp in the reception room below the bathroom shower. If in good shape this house would be worth around £300,000. I intend to get a level 3 survey done to check on this.

However before I proceed with my solictor etc, I asked the estate agent to ask the owner for:

1) any planning permission paperwork for the extension and
2) whether it used to be an airy house and if the walls were rebuilt and if so if they have a PRC certificate.

Yet I have just had a reply back from the estate agent, below is the sellers response.

1) We don’t have any planning permission documents to my knowledge.

2) Again, I’m not sure we have that either, but did the EPC not confirm it was built this way?

So I am wondering what I should do. My solictor would normally go through these questions. But before paying out I thought I could check these points first.

Should I ask them to obtain retrospective planning permission or query an indemnity policy (are these worth while?). Or chase it with the council myself to see if they have details.

With the PRC certificate being missing, should I ask them to pay for a new one to be done? Maybe approx £1,000

Should I just pull out off the sale? I have submitted my mortgage application also.

Thanks

Matthew