Dave Plowman typed:

In article ,
Andy Hall wrote:
Aqualisa suggest a crochet hook but I don't have one of those in my
tool box :-(

Tried a crochet hook - doesn't work.

In the end I used a scalpel with long blade and jjust stuck the tip
into said O-ring and used scalpel as a lever to ping it out.

Maplin used to do a set of 'PCB' tools which had a selection of hooks
and sharp probes. Seen them on Ebay too. They get a lot of use for
things they were never designed for...

I've got a set of Dentist tools from an auto-jumble !
Wonderful hardened tools that must have cost a fortune new, now used for
anything except dentistry.