Front brake calipers - removing both pistons

[aec]

I've got one of my calipers off for refurb, early ATE type with twin pistons. Dust seals were breaking up, but from what I can see of the pistons so far they will be fine when cleaned up, so I have a seal kit on order.

Both pistons are really stiff, I tried using compressed air to move them as seen in various youtube vids but didn't have much luck and got scared so I connected it back to the van and used the hydraulics to push the pistons at the cost of a little fluid.  This is worked and I have got both sides moving, but haven't pushed either fully out yet.

Ideally, I'd like to get both pistons out at once and clean everything up nicely inside an out before refitting, but cant see a way to do this (I've only tackled single piston calipers in the past). Looks like I'll have to pop one side, refurb that, then pop the other side and do that.  It's not the end of the world if this is the only way but thought I'd ask here in case there is an alternative method to get both out that I'm missing?
 

[Aidan]

twin piston new non-exchange calipers of the Girling type are available from autodoc for not much money, the ATEs generally have a core charge, several of the UK Suppliers should have them outright sale too; on the phone app from autodoc you get best price, Mondays often 40% off, spend £150 free delivery takes a week to 10 days generally from Berlin
Bentley doesn't have caliper refurbishing instructions in; iirc Haynes says don't split the caliper so unless they both come out at the same time you will have to do one piston then hold it in place with a g clamp whilst pushing the other side out
for me, mission critical, like brakes, I'd just buy refurbished or new calipers

[aec]

.... I'd just buy refurbished or new calipers

After having done them I can now see the logic in that advice!  Lots of back and forth and mess putting the calipers back on the hydraulics to push out the stuck pistons individually. The pistons themselves cleaned up nicely, the bores needed a bit more work to clean up and that was really tedious without splitting them.  Why are Haynes so adamant that the calipers mustn't be split?  It wouldn't have been a lot more effort to separate them each time to help cleaning, but I went with the advice and left the small o rings in the kit unused.

Still, all done, back on the van with everything moving freely again so all is good