I'm trying to fit a new set of brake pads to a set of Mono Mini's but cant get the pistons to push back far enough to get the new pads and rotor to fit, even after using the old pads to lever thm back, one goes back and the other pops out a bit…

Any tips or bright ideas?

just slacken the reservoir cap & let it push some fluid out when you push the pistons back

Take the reservoir cap off to let any excess fluid out. Wrap a cloth around it to soak any spillage up. If you bleed / fill the brake with partly worn pads you can end up with too much fluid in the system to allow both pistons to push right back

What TJ said.

as above take some fluid out of the reservoir & try to prise the piston back – should be Ok then.

Cheers everyone, i'll be back if i make a mess of it.