Opened up the interior light to look at the aerial fixture the other day and lost the main interior lights. Presumed a fuse had blown but the rear lights were still on. Had a brief look but nothing so i though i'd check the bulb by swapping the rear interior bulb with the front one (not knowing they were different sizes) - In doing so it did blow the fuse and i lost the rear lights as well (not the best of nights)

Anyway i replaced the fuse, gained the rear lights again but i still had nothing from both the main front interior and map lights. Thought for the sake of £2 i'd replace the main festoon bulb and if it didn't work then i would have a spare at least. So I replaced it and still nothing on the main (central light) in on or open door position.

Map lights however suddenly started working and strangest of all, if i put both map lights on the central light then comes on.

Any idea how i can return this to normal or any hints/tips as to why this would be happening ?

thats strange but im guessing that there must be a loose connection somewhere. check your earth wire isnt loose.