Conservatory to extension

[Ellypoo]

I have a south facing conservatory which is a good size & has underfloor heating so is fine to use in the winter, however I'm considering changing the roof to a solid tile roof with insulation- what do I need to consider? Do I need planning permission? (It was previously granted for the conservatory), the bottom of the walls are brick, and there are 2 solid walls (the one against the house and the one that borders on the next-door neighbours garden).
Will speak to builders, but any advice, suggestions etc from anyone else who has considered or done it would be very welcome!

I had mine changed to light weight tiles and needed buildings regs in my area, it needed extra support along the run of windows for snow load calculations. The foundations will need to be checked and you may find they are not deep enough. You maybe advised to start again for a full roof