Do not even consider dealing with these people.

I know this is a late reply but we booked an airport transfer through City Discovery.com for Barcelona airport to our hotel and this was eventually transferred to World-Airport-Transfer.com. Firstly I realize it was silly to even book this as it was so easy to find a taxi big enough to handle our luggage, which was my concern. It appeared to me that most of them were large enough.
We received a confirmation and a voucher and when we arrived in Barcelona the driver was there. He appeared to be a taxi driver and spoke no English and so we couldn't confirm anything with him about the return transfer. No time had ever been established for pickup at our Barcelona Hotel.
We began trying to contact World Transfer.com repeatedly by email two days prior to our departure for a confirmation of an 8:45 am pickup on the day we were leaving. They would not reply.
We tried calling the phone numbers provided for the local Barcelona company Splash travel, the regular and the 24 hour emergency number, and there was no reply at either.
We finally called the World Airport Transfer office in the UK twice. The second time the person answering the phone assured us that someone would return our call at our hotel in a short time frame. We waited about 2 hours and then gave up. There was never any call received from them at the hotel and no email.
We left the hotel at 8:45 am and with no surprise whatsoever noted that there was no transfer driver there. We took a cab. When we arrived home there was an email confirming the transfer in our in-box. It was sent late the night before we left but we had not received this when we left the hotel. Of course the company told us the driver had shown up at 8:45 am and we were not there. If we had received a confirmation from them that the driver would arrive at that time we probably would have waited another half hour or so but because they refused to answer our email or our phone call, we assumed they were not coming. I would think seriously before booking any product through this company.