I haven’t done it, but there is a fuse box in the passenger side footwell, you could easily disconnect the current wiring and run a feed in from one of the switched live fuses. Alternatively you could use the ambient lighting circuit and cut into that, which I think is fairly easily accessed just above the drivers footwell under the steering column.
As i have been in there recently I would caution this - the audi has a heavy duty light holder and dimer low watage bulbs, the jag has a flimsy bit of plastic. if you leave these on full time they could melt.
When the headlights are on if you have them fitted the footwell lights should remain on all the time, what age is your Fpace and what Spec as this may help to advise if you have just standard lighting or the ambient lighting package where the lights stay on.