Ivan,
We visited Christos Apartments in September 05, also with Olympic. A while ago I know, so cannot advise on current position. The apartment was excellent, the pool was super, even in September, and the owner (forgotten his name) was great. There is a supermarket across the road. The walk into Arillas is easy, all downhill. The walk back up again is quite an effort, takes about 20 minutes (along the road, not including shortcuts). Don't be put off by this.
The apartments are in an excellent position, almost equidistant between San Stefanos and Arillas. It is a very easy walk into San Stefanos for a superb beach and a further selection of great restaurants. Not that these are missing from Arillas!. Walk back from San Stefanos is quite easy. Need a torch !! There are also some good walks into the surrounding olive groves.
We would return to Arillas in a second. Just cannot seem to manage it.
Hope this is useful.
Wil