It seems few on this forum know much about buying boats in Spain. I separately posted on same type of theme for Denia or Valencia with zero responses. Maybe there are no reliable brokers in mainland Spain?
Googling "boats for sale in Alicante" gives plenty of leads to brokers/dealers. Not surprised few have direct experience. The number of people in the UK looking to buy a boat there is probably pretty small and the number who are members of this forum even smaller!
Yes -there seems to be 3 brokers as per R.Ems -rather depends your boat sector of course but international network broker like Valk and another Dutch solo operator in Almerimar . I would love decent boats for sale website but that’s rather like comparing Rightmove with some Spanish property sites ,all seems a bit cobbled together in Spain unless you are searching for smart Mobo in Las Palma etc.