You've got me confused again!
Outlook Express isn't a 'site' (as you refer to it in your post). It's a program which allows you to access ANY email service which uses 'POP3'. (All ISP-based email services use POP3, as do the services provided by Gmail and Gawab, but most other free web-based services don't).
If you've not already done so, open Outlook Express and carefully follow the instruction provided in the final paragraph of my first post from the link above.
Then, in future, you'll never need to visit the Gawab site again in order to send or receive email. Simply open Outlook Express and use it in exactly the same way as you would with your BT address. Your contacts list in Outlook Express is completely independent of any particular mail service. It won't disappear when your BT address expires and you can use that existing list with your Gawab address.
When you're away from your home PC (and so can't use Outlook Express) you can still access your mail via the Gawab site, but it's completely unnecessary for 'day to day' use.
Once again, if you're still not certain about something, just ask me and I'll try to explain.
Chris