Dont use any of them, get a taxi from the rank at the airport.
If you are flying to Reus, its only about 10/15 mins in a taxi to Salou.
and its 30 euros or about £20 each way.

thats fine going but how easy will it be to get a taxi back from the hotel to the airport

Hi,
it's very easy to get a taxi at the hotel. Just ask reception to phone for one for you, that's what we did last week.
Jules

I went two weeks ago from Liverpool to Reus via Ryan Air, stopping at the Villa Romana hotel in Salou.
Arrived at Reus at about 10-30 am, on the Sunday morning.
There was at least 10 taxis on the rank, but I caught the bus which is cheaper but takes a little longer.

I got my hotel to book me a taxi for the way back and it cost 28 euros, again on a Sunday.
Depending on exactly where you are staying it should cost around 30 euros each way, the fare is set by the local council or whoever. But agree a price before you get in.

I reckon resorthoppa and the other firms will be more expensive and ive also read a few reports about them being unreliable.

holidaytaxis.com were excellent for us. We were six, so needed an MPV taxi. They were waiting for us when we got out of arrivals, took us to the apartment agency so we could pick up keys and then yook us on to our apartment.

On the way back , they picked us up at exactly the time we stated, so an all round good experience with them.

They were not cheap (£90 for the return trip) but more than worth it for a hassle free experience.