Is there a way of testing if the fuel sender is working by using a multi meter around the back of the instrument cluster somewhere? Ps mine is a wagon. Ta

I might be wrong with this and normally I dont guess if I dont know BUT;
I think the sender is a variable resistor of about 200 ohms or so. If it is open circuit the fuel gauge will read 'no fuel'. The orange low level alarm should still be OK.
The other place you might be able to access the sender is through an inspection port in the wagon floor. Is there an inspection port? Might be easier to probe there rather than the rear of the instrument cluster. I dont have to fiddle with my TW very often, if ever, so I might be basing my remarks on my old TP farm wagon.
I feel sure some one else may have the answer so dont rush in just yet!.

Here's the workshop manual - might help? https://flic.kr/p/FSexiD https://flic.kr/p/Fs7X6b

thanks for the replies.

just clarifying, according to the simple fuel gauge test in the manual, if scenario 2 is true, then the gauge needle will move when the fuel gauge terminal and the earth terminal are connected by a multimeter / test light?

also, the manual gives 3 possible faulty scenarios. what should the test result be if everything is working ok?

What bb61266 has shown is the test for the fuel sender. In your case, with the sender out of the vehicle, when the float is down (ie empty tank) the resistance is between 106 and 108 ohms. If you use a analog meter, you will get a reading between 100 and 120 ohms possibly, due to the way the analog meter works. Such a result is OK. The close tolerance on the given values is the manufacturers production test specification. For doing sanity checks, the result only needs to be near enough.
When the float is raised to the 'full tank' position, the resistance reading will be between 2 and 4 ohms. Again, you will get a result of less then 10 ohms if all is well.
All this is test number one.

In test number 2, you watch the analog needle as you move the float from 'tank empty' to 'tank full'. The needle will move from the left side of the meter scale to the right side of the meter scale. If the meter needle jumps about erratically, there is a problem with the workings of the gauge sender unit. Note that this test can't be done with a digital multimeter unless you move the float VERY slowly. The digital meter only tales about 3 readings per second, so its not the ideal type of meter to use for this test.
Both of these test conditions are taken with the ignition switch OFF.
If you wanted to check the gauge as well, reconnect the sender to the wiring and turn the ignition switch ON with the sender out of the tank. I'd suggest you be aware of the possibility of petrol fumes so block off the hole in the tank. The orange low level lamp should also light up.

Its not clear what your 3 'scenarios' are.

hope this helps.

rumpfy - the 3 scenarios are the 3 tests from the manual - fuel gauge simple test.

is it possible to access the fuel sender in a TF wagon without having to remove the fuel tank?

The manual isn't clear about locations - but try removing the rear seat bottom (two catches on the lower front of the cushion pop it up) - underneath the passenger side is a plastic cover which I think? has the fuel tank connector....

Pretty sure the under-seat hatch is only on the sedan, not on the wagon. Not sure whether it's possible to remove the fuel gauge sender without removing the tank, I suspect there wouldn't be enough clearance. Dropping the tank looks fairly trivial and would make the job much easier. Remember to depressurise the fuel line before undoing the fuel line (undo connector and run engine til it stops on its own).

Luckily I didn't have to go through dropping the tank. The needle on the fuel gauge itself is sensitive to how hard you press it on. If it's pressed on too light or too hard it won't move.