The wiring plugs are a little different too. On the old unit the supply from the car came via a black wire and a red wire going into a six pin plug. With the new one comes a (from memory) four pin plug with a grey wire and an orange wire. Simply cut off the old plug from the red and black supply wires and join the orange new wire to the car's red supply and the grey to the car's black supply using a good quality connector.
Finally, the only real problem that I discovered is that the new style bulb connector is bulkier than the original one meaning the protective cover won't fit on the back of the headlamp. I improvised a seal using duct tape- it's important not to leave the back of the lamp exposed as water will get in and destroy the ballast- this is what happened to the one I replaced judging by the corrosion around it.
I hope someone finds the above helpful.
I have just replace the drivers side ballast on my car today with a new Valeo unit (part # 088318)
The replacement is available from GSF, it's not listed on their site but they ordered it in for me.
This may be a more convenient option than mail order if you have a GSF branch near you.
My branch is always fair with prices & will always try their best to price match.
As you mentioned then replacement unit is supplied with a new power plug as the connector on the new ballast is different to that on the old factory fitted one.
I cut the old plug off & connected the new plug as you did...
Orange of new plug to Red of old plug
Grey of new plug to Black of old plug.
I also noticed that the connector that goes onto the bulb is bulkier that the original, however l was still able to fit the protective cover on the back of the headlamp ok on mine.
The connector pushes on & twists to lock on, you can position the connector in 2 positions, maybe if you tried yours on the next position round the protective cover would fit ok.