Water wont turn off on my electric shower

[davehayley]

I've had a reliable electric shower (triton jade 2) for the last 3 yrs. When coming out the shower today I tried to switch off the water on the shower unit but it continued to spray. I then pulled the cord on the isolation switch but still it continued. At the moment i've isolated the water on the stopvalve but this means the water in the toilet wont fill up when flushed.

Would appreciate any advice :)