Loving Alfie
What cute boy he is
A little leakage into the gaiter is normal, hence there's a leakage return lne on it... There will not be a huge amount but then again, a little LHM goes a long way..
They're easy to replace once the suspension cylinder is removed from the subframe and that's not hard - usually...
Remove the sphere and disconnect all pipes... Then pull out the 'R' clip that hold the pushrod into the suspension trailing arm. After that the cylinder will pull out after manipulating the pushrod.
The big issue in the UK at least, is that 'R' clip can rust so badly that it becomes almost impossible to remove and to do so becomes a real battle involving drilling it out in extreme circumstances
Hopefully, in Spain it won't be an issue but do douse it in penetrating/releasing fluid for a few days prior.
That gaiter must be replaced soon as dirt and grit can damage the exposed piston by scoring and pitting it. Have a good look at it for damage, especially scoring along its length, as such damage can increase the rate of LHM leakage from it and may account for one side appearing to leak more than the other...
Hope that helps and here's hoping your 'R' clips pop out easily!
What cute boy he is 
I needed a very hot coffee or two to revive me!
)