Sadly there is no way to remove a scratch short of changing a panel..
A trick I have used to good effect in the past is clear nail varnish, or in some cases I have managed to find a colour of nail varnish so close to the colour it could barely be seen even if you were looking for it.. And yes, lots of different white available !
You say fairly deep, is it through to the glass fibre, if not and depending how bad it is I might be tempted to say just leave it or if you think it will improve with polish you need a cutting compound and then your preferred wax to finish.
The only way to completely take it out is to flat the whole area down to 1000 grade wet/dry and then polish with cutting compound, BUT you dont know how thick the gel is so dangerous. You could fill it with the same colour and again flat and polish. I would be tempted to just polish with the cutting compound, and I ran a GRP and Carbon Fibre moulding company for 20 years.
When we made moulds we would double gel so that we had plenty to polish and cut back into.
Think it is painted as contacted Bailley and they said would need to be re painted
Will try just giving it a light rub with T Cut or similar then autoglem resin Polish and see if can get the worst of the scratch out