The current arrangement is like this:

The red circle is an elbow, which is about 1 metre below ground level. I can't reach it with my arms if I lie flat on the ground. I can only see the elbow if I put my head slightly into the hole (being careful not to lean too far!). All of the pipes and pump were installed before the finished soil level was known - the tank is about 0.5m deeper than originally expected.
If I'm right, I think Tombo is suggesting something like this:

with an elbow to bring the pipe up to ground level, then a further 2 elbows to send it back down to the pump.
I quite like the idea of having a semi-rigid pipe going from ground level down to the pump to help me position it carefully on the bottom of the tank, but I'm a bit wary about having so many joints. I suppose two of the elbows would be easily accessible in case of leaks...
I'd probably use the Plasson type of elbow in 32mm

rather than push-fit 22mm, though I do have a coil of 25mm MDPE lying around so that would be tempting!
I'm now wondering if this is what Desp was suggesting (3 elbows)...
What does anyone else think?
Thank you!
Yes that's what I was suggesting. Although I'd use a T off the main riser at the hi point rather than an elbow. I'd use the vertical connection on the T to fit a tap or vent at the high point. This could be used for purging air when installing so the pump sinks easily and for testing pressure, flow etc