Losing Data

Hello, I have a Seagate FreeAgent Desktop external hard drive. It has mains power when it's plugged in, but, when connecting it to a computer, it isn't detected anymore. I've tried connecting it to several computers, but nothing works, and I have changed wires to check if that was the problem, but no luck. I have a lot of files on the hard drive and was hoping you would be able to recover them for me as I cannot access anything on it.
I live in Ealing and was hoping you could pick it up as I read you have a free collection service.

My Dell Studio XPS 8100 desktop PC restarted after a blue screen error and then refused to boot with a "No boot device available" error. It's two 1tb Samsung HDDs in a seemingly relatively pointless RAID 0 array of which I think over half was used. Although the RAID volume statuses are "Failed", it does seem to detect both hard drives and this gave me the hope to come to you.
I don't know exactly what's wrong but the replier thought it was a HDD failure.
Also, as I mentioned in the thread, I tried to run the Dell diagnotic tests but now the whole thing won't power on.
Might you be able to recover my data? If so, are you able to provide a rough estimate of the total cost?

Toshiba HDTB105EK3AA USB 3.0 2.5 Inch External Hard Drive – Head is clicking when powered up, and the partitions obviously fail to mount.