Hi,
I just had one of my Diaphragms go. Where the AVAC hose connects to it, it had snapped off. This is quite a common fault and about my 3rd one over several years.
I have tried to glue them in the past but always failed. However I have discoverd that if you remove the inside of a BIC biro pen (that has run out!) and cut about 1cm length of it, it fits perfectly into the diaphragm. Add a bit of superglue around the edge and let it dry. The hose (with the bit of plastic from the diaphragm still in it) then slides perfectly over the bit of biro that is now glued into the diaphragm. Add a bit more glue and let it dry. Then cover it all in sealent just to make sure and give the repair some support! Its a bit fiddly but appears to have worked and is better than buying a new one!
Cheers
Stu

Top tip! I'll try that. Broke both of mine when changing the head gasket, the weather was so cold that the vacuum pipes has become almost solid and the plastic brittle! I have got two new ones, but if i can get the old ones working with your tip then i'll save the new ones. Cheers

Just an update. Tried this tip this afternoon, worked a treat!