You are waiting to exchange contracts with the seller - when contracts are exchanged there is no going back. You have to buy and the seller has to sell at the price agreed.
I would speak to the seller and ask if there is a hold up. Speak to the estate agent as well. Then speak to your lenders and confirm that there are no problems with the mortgage and that the survey is OK.
If there are no problems after you have spoken to all these peole then TELL your solicitor that you want to exchange contracts. Remember he is your solicitor and should be acting on your instructions