I've used CPL. I thought they were very good but I can understand why you are upset with them today OP.
In our case, the sellers solicitor was refusing to answer any of the questions they were asking because my husband was related to the people selling the house and so "he ought to already know the answers." 
He almost made the sale fall through (and cause a massive family rift) because he didn't want to do his job and because, as he told both me and the family member selling the house, he hated CPL and said they could go whistle for their answers.
I've been admin for an estate agent and all to often solicitors have gone on holiday and nobody covers their work and everything is held up, which is one of the reasons we chose CPL in the first place, they do have holiday cover.
When we sold that house and bought the one we live in now, our seller was using the same solicitor and my heard sank. He was again just as rude and useless as the first time we had been in contact with him.
And it turned out that our house needed two insurance policies taking out on it before our mortgage lender was happy, one to guarantee that the off road parking would always be valid as it is reached by a private access road and one to ensure that the building work which has been done isn't in contravention of a clause in the deeds allowing the council to insist the house is returned to it's original design.
All these things were done before our seller bought the house, using this same solicitor, and were things that he had never picked up on when he should have. He was very rude about our solicitor making a fuss about such unlikely things but I think it was all bluster for not doing the job properly himself when his clients bought the house.
He is the reason why we exchanged very late on Friday and moved first thing Monday morning, instead of having a week between them. And it took a threat from me to sue him just for being alive to achieve it (and the complaint to the ombudsman I threatened to put it, which you can do to CPL too)
None of which helps you, sorry (except perhaps the ombudsman bit) 
. But my long and rambling point is, either someone at CPL has picked up on something a colleague has overlooked, which hopefully you can rectify with a quick fax through of the paperwork they need or someone at CPL has overlooked something their holidaying colleague already knows and you should still be able to exchange and complete this week.
Hope things work out quickly for you.