Recently I've noticed that the cold water flow rate from my thermostatic mixer shower has dropped markedly. Flow was previously good, verging on fierce. Hot water provided by the combi boiler and the cold straight from the mains (I think this is the case, but not sure - other bathroom cold taps hooked up to a tank and they still have good flow).
Any ideas from those more knowledgable about the likely cause? Would a simple knackered cartridge explain low flow rate of only the cold water? Not going to fix this myself, but just need some pointers as to what needs doing when I call in the pros.
TIA