It was until recently standard for cabin crew with foreign language abilities to make a welcome PA if there were more than 20 passengers (for that language) on the flight.
I personally think it is a great idea, BA's traffic is made up of 60% non UK people. It therefore makes sense to make the announcements in whatever language is available to the airline, hopefully making individuals feel valued etc.. In my experience, non English speaking passengers really appreciate you "having a go" and explaining this to them in their own language.
BA even have the safety demo and safety related announcements in other languages.
It is actually very gratifying being able to speak to other people in their own language, and they certainly seem to appreciate the effort you put into it. I speak good Spanish, good French, a little Greek and some Sign Language. It is also a great tool to use to let customers know "we are not just trolley dollies", but have a decent education and can put it to good use.
I recall one flight where a passenger said to one of my crew "I bet you wish you had gotten better grades at school now, eh? Then you could have a proper job"
Passengers are a law unto themselves................