The tower houses a ring of 12 bells cast by the famous Croydon firm of Gillett and Johnston Ltd. in 1936, replacing an earlier ring of eight. The eight original bells were recast and hung with new fittings in a new frame with four additional trebles.
The new ring of 12 was dedicated by The Right Rev Lord Bishop of Croydon on 12th December 1936 and the first peal on the new 12 was rung for the Coronation of King George VI in 1937.
There are now actually 14 bells - a ring of 12 with 2 extra bells. An extra 'flat 6th' was added in 1946 by Gillett & Johnston, which allows the use of a 'middle 8'. An 'extra treble' was added in 1978 by the Whitechapel Bell Foundry, which allows the use of a 'light 10' and 'front 6'.
There is more information on the Croydon Ringers website.