You asked

I am looking for data relating to property chain length – specifically:

Average length of property chains in the UK (i.e. number of individuals in a chain)
Broken down by region if available/feasible

Maximum length of property chains in the UK
Broken down by region if available/feasible

Transaction completion rate by number in chain
By “Transaction completion”, this means the percentage of buy/sell transactions completed.

We said

The Office for National Statistics (ONS) does not have any data on the length of property chains. The statistics ONS publishes showing the number of residential property transactions are calculated from Land Registry data on individual property transactions. These data do not contain any information about the relationship between properties in a chain and so, unfortunately, it is not possible to produce statistics on the length of chains.