What an absolute disgrace the law is with regard to buying property. The prospective buyer does not have to make a cash deposit, even a modest one, to show good faith. Some 'offers' are made by people who are in a long chain of unknown people, with unknown finances. In my experience, Estate Agents are less than honest about this issue and solicitors don't feel it's their responsibilty to check the chain. Teamwork between solicitors and Estate Agents in non existant. Timescales may be mentioned, but there is no legal timescale for Exchange of Contracts or Completion. No wonder it all goes wrong - unless you have a cash buyer, and that doesn't always work either.
The last time I sold a property I made it clear that I wouldn't accept any prospective buyer who had a long chain behind them. Its better to be fair at the start.
When someone was found, I asked the Estate Agent to verify that they had a deposit, a mortgage and evidence of any other finance needed. The Agent did do that, and the sale went through.
This sounds harsh, but would you buy a car expecting not to pay a cash deposit, not providing any proof of how you would pay the full amount and not being able to stick to a timescale?
In Australia, once you make an offer on a property, you have to have a survey within an agreed time. If that is acceptable to you, you do then have to agree a date for Completion and pay a deposit, which you will lose if you back out.