Peter I hope you are not using actual jubilee clips but proper fuel hose clips, there is a difference. Jubilee clips (worm drive) do not clamp the hose with even pressure all round.
Tim
Don't worry Tim they a proper fuel hose clips. They may not be Jubilee but Jubilee actually do make fuel hose clips.
http://www.jubileeclips.co.uk/products/jubilee-juniors/Then there are the Original Jubilee Clips
http://www.jubileeclips.co.uk/products/original/Interestingly the Original Jubilee Clips are rated for a higher pressure than the Jubilee Junior clips.