The West Brom is the seventh largest building society in the UK with most of its branches located in the Black Country and Birmingham but is also serves mid-Wales and Shropshire.
Hampden & Co operates from offices in Edinburgh and London. It was established by a team at private bankers. It expects to welcome its first clients during the first quarter of this year.
Stafford Railway Building Society, established in 1877, operates from a single office in Stafford.
The CML now has 126 members, a further eight members that are third party administrators and 76 associates.