Have you got the breakdown of their bill? They should have sent you one listing what they did and the fees included for each search and request they billed you for.

Then polotly tell them to fuck off.

Then go and find the official place to make a complaint as if thy are barging you for something that's gone up after you were supposed to have had it done then what else have they missed?

My uncle got back his £40k court costs and the £7k he had to pay for an error his soliciter made about 15 years ago that only came to lighting the last few years so deffo worth pursuing if you could potentially get shafted when you come to sell the place.