Franchi Borlottie bean (di lamon) - poor germination

I bought a packet from (from RHS).
They rotted.
I bought another packet from (from RHS).
I gave ten to a lady who usually excels (I give her anything which does not work for me) and she only got two to grow.  I tried mine in a number of ways (drenched with Murphy’s compound, lying on damp sand, in peat, straight in earth) but very few made it.
The few seedlings that did make it are feeble specimens.
Has anyone else had any experience of this?
I could complain from RHS but getting my money back is really not the point.  I want plants!
Can anyone recommend a source/method that has worked for them?
TIA,
   Bill