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:

http://tinyurl.com/y45typw9

Should I fit one or is it overkill?