There is at least one on a preserved line, though not at a location which is immediately obvious....
The signal box at Welshpool Raven Square contains a 16 lever frame from Groeslon on the line from Caernarfon to Afon Wen. Only 5 are in normal use (4,5,6,14 & 15); there are also levers controlling the crossover into the bay platform plus associated facing point locks. Currently out of use are levers for the home signal and bay platform starter.
There is a long term plan to demolish the rather ugly signal box and build something more appropriate on the opposite side of the line.
The box is normally operated by the fireman who is busy getting the fire ready for the Golfa so if you wanted to measure/photograph it the Raven Square stationmaster would be the person to ask.