Random lighting fault

Hi there

I currently drive an Octavia MkII VRS estate and am experiancing a random lighting fault where I have lost at least one of each light/indicator on each side front and rear? This happened about 1 month ago and after changing many bulbs and disconnecting switches/light clusters etc they suddenly came back on when moved the headlamp dimmer switch and then could not get it to happen again. The car was fine for around a month and has now happened again but intermittently with no logic at all, will come on or off while drive and/or when start ignition? 

My helpful local mechanic has helped me although now unsure where to go from here, we have disconnected the BCM unit and reconnected but although it did not instantly make lights work they did later come on so our next thought is to replace this unit although at £220 +vat it is not cheap. The number on the unit is BCM 1k0 937 087 D 

Hopefully somebody has experienced a similar issue or can give me any advice at all?

Thanks in advance

James