since living in the current house we have had a Mira 415 Pressure Balancing shower. It works fine - no temp fluctuation due to someone flushing a toilet.
As part of our refurb I am looking at replacing it and find it is no longer made so I will end up going for a more conventional bar type mixer.
Concerned about pressure fluctuations I did some Googling and found this:
formatting link
Should I fit one or is it overkill?