As beddhist says, if you use Leaded fuel with a bike that has a CAT fitted, you'll probably damage the CAT.
At the end of the day though, if you need petrol...you need petrol, whatever type it is!
When I visited Morocco a while ago, I ended up using Leaded fuel in my Yamaha. It shouldn't cause any engine problems (in fact the bike ran very well using it). In the UK, they don't check the emissions of the bikes during an MoT check (I'm not sure what they do in Europe), so nobody would ever know if the CAT wasn't working correctly...
Have a great trip!