'The (Plymouth) Brethren' in Pre-war Hong Kong

I've come across a reference to 'nightly prayer meetings run by the Plymouth Brethren at the Duddell Street Gospel Hall' in 1941 (Ted Ferguson, Desperate Siege, 30).

Does anyone know anything about 'the Brethren' in pre-war Hong Kong? Or about the Gospel Hall? For example: where exactly was it? Was it used exclusively by the Brethren or was it available to any Evangelical Christian organisation?