I pronounce it the same as seahorse- Ba-len-sea-a-ga with the accent on the "len"
Miss alice is completely right though. My friend Alicia is from Madrid and her name is pronounced "Ah-Li-thia". She always corrects me when I say Ba-len-sea-a-ga and tells me it should be Ba-len-thi-a-ga. I still pronounce it my way because when I asked "when the A/W 06 Ba-len-thi-a-ga bags were coming in " at Harvey Nicks, all I got in reply was "Eh?? Do you mean Ba-len-sea-a-ga.... snigger....snigger"- implying that the SA thought I was a complete and utter thicko"