Using 3G data card

[Badger]

I need to use my laptop abroad, both for emails and general internet stuff, but I dont have access to an independent telephone line/broadband connection. (telephone in apartment is billed via Reception switchboard)
I want to use it in my apartment, not sat somewhere outside trying to find a hot spot.
It has been suggested to me that I could put a 3G data card into my laptop to give wireless broadband, but I presume the charges will go through my mobile?
I am on Orange pay as you go (I know thats sad) but when in Spain I use a spanish sim card in it for cheaper calls.
How will that be affected, what sort of charges are made by the phone companies for this facility and am I still better with a spanish phone no. as it is with the sim card I use at present?
Even though we are away for 3 months I still have my broadband connected on my home computer, is there any way I can have any connection abroad via that?
I'm really not very computer literate so apologies if these are very basic questions with blindingly obvious answers. Thanks.

[dmjarvis]

I think that you will pay the appropriate call cost for your operator and location, but you will also pay for the amount of data that you send/receive whilst online. This could work out to be a considerable cost, event if you're only online for 5-10 minutes at a time.