2004 Renault Megane 2 Windows will only go down - relay problem?

To give the full story...

I returned from holiday last week to my Renault Megane under about a foot of snow having been left in a car park for a week when all the snow hit the UK.

When I dug the car out, got over the shock of it starting first time and not stalling ever foot I tried to move, and got out on the road, my passenger wound the window down to clear ice off the wing mirror. When he tried to wind it back up, it wouldn't go up. I then tested the driver side window (mistake), as it went down, but when I went to wind it back up.... it just went down further.

I'll skip the story of how I got the 280 miles home with no windows to present day...

With still no windows down, the situation was that you could here something engage when pressing the buttons (passenger and driver side, but nothing happens). The lights on the interior even dimmed when pressing the buttons, so it seemed to be trying to do something.

I took it to the garage and was quoted around £600 to replace both side window regulators and motors. Ouch, I thought I'd have a go myself.

I read through several posts on here and other forums suggesting ways of getting the window to wind back up (deadlocking, fuses, batteries etc etc, but to no avail) so it was time to take things to pieces.

Having dismantled the drivers side door to get to the window regulator (as I've read on here and in many places that this is a common cause of such faults), I found this to be all fine. When testing the mechanism, the motor also seems fine. The issue is still, that no matter which way you press the button, it winds in the same direction (down!). I'm pretty certain that this is the same fault on the passenger side.

I wonder if this might be the black box attached to the motor, or possibly the relay on the circuit?
I've tried a heat gun on the black box thing where the coil is (another suggestion I read), but that didn't work.

Where can I find the relay for the windows so I can check if this is OK?

Is it possible to buy the motor/black box thingy separate to the regulator? It seems you can get the regulator separately, but I cannot find the other part anywhere.

The car door is currently in bits, as is the regulator, so if anyone has any advice on how to put that back together, that would also be helpful!

I've had so many problems with this car. As soon as it's fixed, it's going!!

Any advice greatly appreciated