New to Mobile BB - help

[Daisy]

I have just bought an Archos 5g Internet Media Tablet. It works with wifi and 3g networks.

You need to put a sim card in it for the 3g.

I already had a ZTE MF622 USB modem that I bought off someone a year ago and have never used with my laptop. I took the sim card out of the dongle and bought a Pay As You Go Lite £10.00 top up voucher. I was unable to activate this voucher on line with 3 Mobile because they ask you for the number of the 'phone' and, of course, it wasn't going in a 'phone'. None of the help contact emails or phone numbers on the 3 mobile site worked without a 'phone' number. I went to the 3 Mobile shop in town and they looked up the number for me (quite which 'phone' number this is I don't understand but it worked and I was able to activate the voucher). I am now able to use the internet, do emails, watch web tv, etc, on my Archos 5g.

My question is, having never used mobile bb before, when my 1gb allowance is used up will it just stop working, or, if this is before the 1 month expires will I be charged at a higher rate, etc, until the end of my Pay As You Go one month is finished? Also, I'm not really sure what constitutes a 'download' - is it only when you actually download a eg program, song, video, etc.

While I was in the 3 Mobile shop I asked about using it during my 2 week holiday in Spain soon (I'm in UK) and the answer was 'don't do it'! When I tried again, I got the same answer. Now I have read some horror stories about running up huge bills but I would like to know what I would need to do to use this Archos in Spain and roughly the costs involved.