Thanks people. I found an old thread which recommended the Park tools pliers so I’ve ordered a pair. £19 but I’ve tried a few others that I’ve bought and borrowed with no joy so thought I would get a decent set that hopefully last a long while.
The Park ones lasted exactly no goes. The tips snapped off first try. I hope you have better luck.
I think I eventually got a mixed set from Screwfix. Though at the time I might have resorted to a couple of thin and long and pointy things and ‘chopsticked’ the circlip out. PITA.
I replaced the 💩 sram plastic pistons with some Al ones off of eBay.