1996 Triton aqua sensation thermostatic mixer shower cartridge removal?

Triton aqua sensations thermostatic flush fitting mixer shower was installed in 1996, it recently stopped giving hot water I would like to repair it if possible because it is a major operation to remove it and fit another type, does anybody know if this shower has a thermostatic cartridge that could be cleaned or replaced and where I would get one as the shower is so old, Thanks in advance if you can help on this one, Regards George.