I made the original water intake manifold intake out of copper but I was unable to get the jubilee clips to close down enough to form a reliable seal. Even after wrapping with loads of PTFE tape the tube proved too wide and the reinforcement wire too strong.
The next option was to use 1 1/4" waste pipe but this was a tad to large for the ID of the tube.
I tried heating it with boiling water but this was not enough as the reforcing spring inside the tube wouldn't give. So I tried the cooking oil trick again. This can be heated much hotter than water and did the trick softening the tube nicely.
Stretched and cooled over a spare bit of pipe
I must repaint the bilge again!
The green pipe is a hose to supply water to test the joints. Water tight now :-)