Reus is very close to Salou. It's definitely the nearest airport.
According to the Reus airport website, the only scheduled flights from the UK are with Ryanair, out of Prestwick, Liverpool, Luton and Stansted.
For bus timetables between the airport and Salou, go here:
http://www.autocarsplana.com/
Select the English option, then 'line services'. Click on 'Base Costa Dourada' and select from the menu.
However, based on the sample taxi fares shown on the airport website (which don't actually include Salou), it's evident that a taxi wouldn't cost much more than �20.
Car hire companies, based at the airport, are listed here:
http://www.aena.es/csee/Satellite?cid=10488589 49358&pagename=Estandar%2FPage%2FAeropuerto&SM O=3&SiteName=REU&c=Page&MO=3
If you can't find flights to Reus, your next nearest option is Barcelona (El Prat), which is about 60 miles from Salou.
Chris