Rear o/s droning

So there's been a droning noise present for the last couple of weeks, and became more evident after doing some work to replace an oil seal on the rear diff.
The droning is more obvious around 35-40 mph, I've had a look at the tyres and there's no obvious sign of stepping.
I had noticed the CV boot had come off, the clamp has completely deteriorated and the joint lost the majority of grease but I re packed and secured the boot again. There was also no obvious play in the cv joint other than the usual lateral movement.

I've also checked the wheel for play but there no movement there.

My question is has anyone else experienced this before. Could the bearing be making the noise despite there being no play. I don't mind throwing money at it to get it fixed but obviously I wanna get it right rather than replace a part that's not faulty.

I was just going to let it develop but it's really starting to annoy me now
Any help would be greatly appreciated

it was repacked with high temp high impact grease, wasnt the same as the green CV grease thought but was the best i had at the time, planning on trying to get some CV grease and re-doing it.

think i'll take a gamble on the wheel bearing and just do it. its trying to find the part, on quattros are the front bearings the same as the rear?
When looking on euro car parts theres a part listed as front/rear but when you look at the specs it just says fitted: front