1:18 am update: it didn't work... will try again later on today... zzzzzzzzz!
Update 22/03/2012: So it didn't upgrade to the icecream version - just the latest Gingerbread 2.3.5 version, which is S*** and should have upgraded last year! :( Oh well. Need to root my phone again toooooo....!!
Update 23/04/2012: At last T-Mobile!!! I finally get my upgrade to Ice Cream Sandwich. ^^
Update 06/06/2012: If you decide to root your phone, follow this person's guide. I found it relatively easy compared to the previous way of rooting!
If you need to download Samsung Kies to upgrade (in the UK) here's the official link: http://www.samsung.com/uk/support/usefulsoftware/KIES/JSP