Also just want to back the last two posters up we went with ICR in September and after we found our driver at the airport it only took us about an hour and a quarter, it cuts out that stop half way, but you did ask for a cheap alternative, as i said i don't have any other info on shuttle bus.
The ICRtransfer will cost you £100 for up to 4 passangers return they will pick you up and wisk you to your hotel/apartment within 1hr 30mins they will only stop if you want to
There are a few threads about their transfer services for you to have a look through
If you do book with them you will not be dissapointed at their service
the link below is their booking form