We moved recently and, yes, it was a nightmare. Our solicitor spent days chasing planning permission for a garage that had been up well over 20 years and an extension that wasn't an extension but merely an old "coal hole" knocked through to form a small rear lobby. We eventually gave her instructions to proceed without this, only to find all the information she had been requesting, and was unable to obtain, safely enclosed with the pre-registration documents we received from the sellers' solicitors after we moved in.
The whole process was incredibly stressful and we did, in the end, give an ultimatum that we would pull out if exchange didn't happen. Sometimes you just have to be firm and decisive. The Estate Agents are definitely the ones to pressurise, they don't like seeing their commission disappearing, whereas the solicitors will get paid regardless.
Good luck. I hope it sorts itself out and you're happy in your new home.