Actually it is a high pressure sytem, frequently running off an eletric in line pump.
Spares availability good but shop around.
Always seizes in hard water areas - regularly. Easy to work on. If in doubt Mira will send diagram.
Plastic bush strips in control lever - you can turn this around to extend its life but you will need a new one eventually!
Mine seizes now so often I probably need complete new innards.
To unseize...strip (the unit too), de-scale until the brass is a light, clean colour with no deposits. When you look at it it looks fine but after a descale/clean it will operate 100% better.
Perhaps an expert plumber can advise whether a water proof lubricant should/can be appled to the workings to stop it seizing.
tinonline
August 2011