If the UV joint is making that noise up on the stand and sounds iffy, imagine what could happen when it's revolving thousands of times an hour, under load.
The joint is obviously notchy. If it were my bike, I'd be making a beeline to Mikeyboy for a professional opinion and possibly a fix. If you do this as soon as possible, it may be fixed before your trip. Dither and you could be in trouble. What I would say, is that you'd have to be lucky to find the right mechanic/engineer whilst in Spain to get a fix on the road. Also, peace of mind is important. You know it's not right before you set off. It's going to be a constant worry as to whether it lets go whilst you're riding.
Good luck whatever you do. Hope you get it sorted.