I tried to do the same on my GT.
The replacement LED festoon ones for the roof were not bright enough and I ended up swapping back. Also they made my colour vision seem off, probably too blue and very different from the yellow incandescent bulbs.
I stuck another white LED in the glovebox and that's OK. The bulbs in my visors are tiny and I haven't bothered to research the size yet.
Also tried an LED festoon in the boot, again not bright enough and swapped back. The festoon bulbs were also awkward to fit as I got 38mm length and they should have been 36mm.
I've got other plans for the boot if I ever get round to it (a strip of warm LEDs that are left over from under the kitchen cupboards)