The next step is the first legally binding one: Contracts.
The vendors (people selling) will draw up contracts of sale with their solicitor. This is a long document - about 30 pages roughly - which has a hell of a lot of legal mumbo-jumbo which all comes down to "We give you cash, you give us house".
What they send is a draft contract, and they send that directly to your solicitor. Your solicitor will usually send you some notes on it and maybe some questions. For example, ours asked us to check the land registry documents referred to the right land with the engineer who did our survey.
Normal procedure is that you will go into your solicitors office and sign both the loan offer (see step 12) and your sale contracts at the same time in their presence. They send these back to the vendor with a bank draft for your outstanding deposit (Step 14). Usually at this point your solicitor will confirm the charge for their service - the start of your money disappearing!