I need to replace the left side sidelight bulb but after partially taking the headlight unit out, I cannot disconnect the power lead in order to fully remove the unit. 

Any ideas welcome

Yes, mine were a b17ch to disconnect the plug / leads also.

I think I ended up breaking off the securing tabs through frustration, but got them disconnected in the end and have not had any issues with the plugs coming apart with the securing clips missing.

Someone may have a diagram of how to un-clip the securing clips but otherwise iirc I just prised them apart with a screwdriver, hence breaking the clips.

Have you googled it???

Try pushing the connector further on before trying to release the clip/connector

Having done just that I can confirm it's the connector that's a tight fit and not the locking tab that's the problem.

 

The best method I found was to pull the unit out as far as would allow both hands around the back to push the plug out using both thumbs and forefingers having first applied outwards pressure with one hand whilst pulling the tab with the other thumb.

 

If you doubt the tab has released just push the plug back on and you'll hear it click back.

 

I found I needed to twist the unit to the side for access and use my knees for support, spraying WD-40 or similar on the plug may help future disconnects.

I agree with the WD40 suggestion

 

 

We once had so jammed only two pairs of pliers, one held by me on the plug, the other by the wife on the plug housing, coaxed it loose by slowly wiggling it.

I have the exact same problem; connector refuses to come apart.  I can't see how the locking tab works; does anyone have a picture?

14 minutes ago, cheadleskoda2 said:

does anyone have a picture?

Apologies for the less-than-photo-studio background ...

 

From looking closely at the connector and many previous tried to separate them on the car I don't believe the apparent locking tab is real.  It certainly doesn't move.  There may be a super-magical Skoda tool that somehow clips into the moulding but nowt I'm aware of.

 

The moulded bump on the socket (on the headlamp) is just a solid bump.  When you push the plug down firmly the bump engages with the hole in the side of the plug but I can't see ant moveable tag or clip as part of this.  I've learned to insert a right-angled plastic trim tool into the gap at the bottom of the raised 'bar' shape on the plug and gently start to lever the plug off.

 

2 hours ago, MikeTheThinker said:

The way I used to do it was pull the headlight out then put my finger nail in the slot by the back of the plug as shown below. Push the plug towards the socket as if pushing it together, press down with my finger nail on that slot, then pull the plug apart. 

 

 

Thanks for the pics and the advice, I finally got it undone with some brute force and ignorance!  The plug and socket came out together so I could then separate the 2 parts and it was easy to push the socket back into the lamp unit.  Spent about 1 hour in total just to replace a sidelight bulb!