House prices are very different across the country. London is always its own bubble, but a crash there will filter out across the country over the next year or so.
If you go to the north or to parts of Wales you can still pick up cheaper properties, in the South West for example you can't easily unless you buy a shared ownership property.
House prices may drop and it happens. The two biggest issues are the higher rate of stamp duty for second homes and changes to Landlord mortgage relief on rental income. If the market crashes, the government could remove one or both and that would help the market.
If house prices drop, unless the property has to be sold (repossessed, owner died or gone into care, relocating etc), a lot of owners will hold tight and not sell. Landlords will not flood the market as why would they - they are still getting the rental income.
No-one will want to be in negative equity (most could not afford it) so will do what they can to hold tight.
The only way to have a 'proper' crash would be for prices to be reset and mortgages cut as well (i.e. your house is worth 20% less so your mortgage is cut by 20%) but that would never happen - it would cost too much and banks would go under.