I discovered a severed wire hanging under the drivers seat, easiest to access from behind (the rear footwell), what did it do?

It has two wires, one red, one black, inside a somewhat-stiff black plastic sheath.

The power-seat works perfectly, so it is not that.

Potential guess: The seat heater warmth is barely noticeable but kind of works (possibly psychosomatic though), so maybe it is the cushion-half of the seat heater?

Also possible: neither cigar lighter had worked but I replaced a burnt fuse that was causing that (but have yet to check if the good fuse actually fixed the issue), do the lines for that run from the center console under the driver's seat?

the ciggy lighter loom runs up inside the centre console, so no it's not - it'll probably be your seat heater power.

Thanks, any idea how many wires attach for that? (as in, are cushion + back separate or one current source?

Could it be a source-supply for the heater-relay under the seat?

Yes!

Sounds like a seat heater to me! Mine was broken because of a broken wire & it worked after fixing the break

It is where the power comes from the lower seat cushion heater, and goes to the seat back heater. With that wire broken, neither element will heat. Even then they are not good, see this post for the cure- http://https://www.jaguarforums.com/forum/showthread.php?t=44965&highlight=seat+heat+solved

Hope this helps, but looks like avt is right

Yup, it was the seat heater! All fixed and toasty now! A bit embarrassing that the previous weak-seat-heat perception was entirely placebo, lol...

I basically did the same thing as Steve except my wires had pulled out of the harness connector so I had to pull out the tiny metal contacts from the connector and solder on new wires and then used wire nuts to connect to the original wires.

It's lovely to hear your problem was fixed , keep enjoyin your ride

So I also have the problem with the seat heater and decided to take a look at the wires underneath my seat.

In this picture, you see the black and red wire along with the yellow connector. I found the red wire was disconnected from the yellow connector. However, a piece of the red wire is still in the yellow connector.

Any suggestions on how to fix this? It appears the red wire is really tight and does not appear to have any slack.

Thanks,
Abe

The easiest is to cut the connectors off and splice the existing wires with additional wire.

So I spliced the wires together after removing the seat. I also noticed that the wire running from one end of the grid to the other was no longer connected. You can see what I mean by the the pictures below. It's too warm here to see if the heater works, but will this prevent the seat heater from working? I'm thinking if it does not work, then I can bend the seat grid towards the wire running across to make the connection.

Thoughts?

I just wanted to know what this wire goes to can I send a pic

We're does this wire goes