Only just seen this. Despite studying in UK Greek O’level with the wonderful Karen Rich (sadly deceased) and using Greek Language and People book - probably out of print now, but I still dip in and out of mine. Also Karen co wrote a book for the BBC with cds.
Since returning to Crete I have found the duo lingo site quite beneficial. I particularly like the wee tortoise symbol on playing back phrases. It repeats at a slower pace and I find that I can hear the stress of the word much better and know where to place the accent. Also free and easy to use. I am trying very hard to at least relearn what I have forgotten! Good luck.