The main advantages of using a Slingcatcher are (a) it frees up your PC and (b) you get a remote control (included with the Catcher) -- ideal for a couch potato!
Slingbox Solo or Pro? Solo is a later model, but either would do the job. If you plan to also watch the feed on a smartphone or an iPad, better to go with the Solo.
If you decided to go the SlingCatcher route, I suggest you buy it in the UK (available from Sling and also Amazon et al) and take it with you to Spain.