How can I stop water dripping ?

You'll probably need to replace the shutoff valve.

Its strange you missed this result when you did your search to help yourself before posting here:

https://www.mirashowers.co.uk/support/fault-diagnosis/

Spares here:

https://www.showerdoc.com/shower-spares/mira (That site is well worth bookmarking. Also note: changing a flow valve is relatively straightforward but can be a bit of a pig sometimes)

xxx
February 2017