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IIRC, you CAN get the switches out, disconnect wiring, then it comes to bits for a new bulb, which, again IIRC, is available from Maplins etc. Not too difficult either, apparently, but I've not done one yet.
All switches light up inside when you have side lights on.
I found the easiest and safest way to remove switches, is to remove complete suround (4 screws), then release from behind.
IIRC dealership will charge around 3.50ish for a new plug straight in lamp. RS components do a pack of 10 for a couple of squids, tiny bit awkward to solder in to the old lamp holder though.