300tdi Disco air leaking into fuel system

Hi everyone and sorry if this has already been covered on another thread but i couldn't find anything. I have been having a reoccurring problem with fuel starvation due to air leaking into the fuel system somewhere.
The problem started after replacing the sender unit, the guy that did it for me put the pipes onto the sender unit with jubilee clips as he said the old parts were so corroded they crumbled as he took them off. The sediment tank had previously been bypassed so i now have a clear rubber hose going from the sender unit and joined where the sediment tank was.
If i bleed the system it will run fine for around 10-20 miles then start to cut out on me, it will tick over but as soon as the revs go above 1500-2000 it dies. you can see lots of tiny bubbles almost like foam going through the fuel line as it comes out of the sender unit. The mechanic says the sender unit is the problem, but it is new and has worked since it was fitted. I am thinking about replacing the fuel line with a single rubber hose from the sender unit to the lift pump, do you think this would be worthwhile before spending another £65 on the sender unit?
Any advice would be very much appreciated as my disco has been parked in the driveway for a month now and i am having to drive my wife's picasso (not good).
Thank you in advance

id be surprised if it was new sender unit ,but possible ,id run a new pipe from passenger side pipe on sender to lift pump as its the only one under suction,worth checking lift pump to ,bleed system by slackening front banjo bolt on pump 13mm socket

Thanks for that, the lift pump has been done about the same time as the sender unit was replaced.
Is that the banjo bolt on the injection pump to bleed the system, i had been loosening the injectors and bleeding it there. I think i will just order about 5m of fuel hose and some new clips to hold them on, it will be much cheaper than and new sender unit. Would you happen to know what size hose i will need?

yes on injection pump, even though pump will self bleed its best to remove it ,air can damage pump,5/16 or 8mm,you only need to worry about that hose unless other leaks fuel out

Thanks again for that i will get the hose ordered and hopefully that should do the job. There is no sign of diesel leaking out anywhere so i dont think the return line will be a problem.

not got the supply and return pipes wrong way round on the tank pickup?
edit
if you got bubbles at your plastic pipe attached direct to sender, then it points to either dodgy jubilee'd connection or faulty sender.
or not enough fuel in tank!

I am sure the pipes are the right way around as you can see which way the fuel is flowing through the clear pipes, also the fuel tank is 3/4 full so dont think that is the problem.
I have ordered some new fuel pipe and hose clips so will be replacing the jubilee clips with those, if changing the entire fuel line and hose clips doesnt work i will have to try another sender unit. If that doesnt work i think i may be calling the scrap yard.

where in west yorks are yer?

I'm in Wakefield