Vintage Minor Register

I have just replaced the master cylinder on my mums rover P3 '60' and cant get it to bleed. The work was done due to loss of pedal resistance and braking, it only has hydraulics on the front, the fluid will drip out of the splitter union and with an airline on the resevoir it will bubble at the cylinder unions. With the cylinder unions undone the pedal just produces bubbling air out of union and then a rasp as it sucks back in. Cant get anything out of the bleed nipples and have checked they're clear. Any ideas? airlock? collapsed hoses?

Toby,
Had similar symptoms on my Series Land Rover.......due to collapsed flexi hose. People had warned me this could happen with flexi hoses but I never believed it until I saw it with my own eyes.
I have a similar problem at present with my MG B. Nothing coming out of either rear bleed nipple, depite new nipples, pressure bleeding etc. Suspect central feed flexi on that as well, but have yet to investigate.
Seasons Greetings,
Paul.

sesons greetings and many thanks for the suggestion.

Ah, note that it will suck in and push out bubbly ait at the cylinder end of the flexihose so probably not collapsed hoses? I'm really scratching my head on this one!